Barack Obama has said he is now within reach of becoming the Democratic candidate for the US presidency.
Barack Obama says he is now within reach of winning the Democratic Party's nomination to run in the US presidential election in November.
Mr Obama has a majority of "pledged" delegates, who are won in primary elections, although he is still short of a confirmed overall victory.
Senator Obama has a majority of "pledged" delegates, who are won in primary elections, although he is still short of a confirmed overall victory.
US media have projected a win for him in Tuesday's Oregon primary.
US media have projected a win for him in Tuesday's Oregon primary contest.
But his key rival Hillary Clinton has won Kentucky's Democratic presidential primary by a large margin and vowed to fight on.
But his rival Hillary Clinton won Kentucky's Democratic primary by a large margin and vowed to fight on.
'Popular vote'
'Familiar lines'
Mr Obama chose to address his supporters on Tuesday night in Iowa, scene of this year's first presidential selection contest.
Mr Obama chose to address his supporters on Tuesday night in Iowa, scene of this year's first presidential selection contest.
"We have returned to Iowa with a majority of delegates elected by the American people," he told his supporters.
"We have returned to Iowa with a majority of delegates elected by the American people," he told his supporters.
DEMOCRATIC DELEGATES Total delegates (pledged and super-delegates) needed for nomination: 2,026Total pledged delegates at stake: 3,253Total super-delegates at stake: 797Total delegate tally for Barack Obama: 1,940Pledged delegate tally for Mr Obama: 1,633Total delegate tally for Hillary Clinton: 1,759Pledged delegate tally for Mrs Clinton: 1,480 Source: Associated Press, as of 0420 BST on 21 May
DEMOCRATIC DELEGATES Total delegates (pledged and super-delegates) needed for nomination: 2,026Total pledged delegates at stake: 3,253Total super-delegates at stake: 797Total delegate tally for Barack Obama: 1,940Pledged delegate tally for Mr Obama: 1,633Total delegate tally for Hillary Clinton: 1,759Pledged delegate tally for Mrs Clinton: 1,480 Source: Associated Press, as of 0420 BST on 21 May
"You have put us within reach of the Democratic nomination for president of the United States," he added.
"You have put us within reach of the Democratic nomination for president of the United States," he added.
The nomination process is complicated because the total of 2,026 delegates needed is made up of pledged delegates and super-delegates.
He also congratulated his opponent, saying Senator Clinton "has shattered myths and broken barriers and changed the America in which my daughters and yours will come of age."
The latter are party elders who get an automatic vote at the party's nominating convention and are not bound by election results.
The BBC's Jamie Coomarasamy, who was in the audience for Mr Obama's speech, says it was a pretty flat event, with a lot of familiar lines.
The crowd was pretty enthusiastic, hoping for a victory lap but not quite getting one, our correspondent says.
In the primaries so far, Mr Obama has secured more of the delegates who will choose the party's nominee at the Democratic National Convention.
He will be hoping that his newly-secured majority of "pledged" delegates - won via primary votes- will persuade the remaining undecided "super-delegates" - party elders who get an automatic vote at the convention - to rally behind him.
'Popular vote'
Hailing her Kentucky victory, Mrs Clinton said she would fight "until we have a nominee - whoever she may be".
Hailing her Kentucky victory, Mrs Clinton said she would fight "until we have a nominee - whoever she may be".
Speaking to her supporters, Mrs Clinton said: "It's not just Kentucky bluegrass that's music to my ears, it's the sound of your overwhelming vote of confidence, even in the face of some pretty tough odds."
Speaking to her supporters, Mrs Clinton said: "It's not just Kentucky bluegrass that's music to my ears, it's the sound of your overwhelming vote of confidence, even in the face of some pretty tough odds."
And in a passage seemingly directed at the remaining undecided super-delegates, Mrs Clinton argued that she would be "best positioned to win in November" against Republican candidate Sen John McCain.
Barack Obama claims election milestone
And in a passage seemingly directed at the remaining undecided super-delegates Mrs Clinton argued that she would be "best positioned to win in November" against Republican candidate Senator John McCain.
Mrs Clinton also said she was "winning the popular vote" over Mr Obama.
Mrs Clinton also said she was "winning the popular vote" over Mr Obama.
The claim has been questioned by the Obama campaign, which argues that Mrs Clinton's popular vote calculation includes disputed contests in Michigan and Florida, and does not include results from several caucus states in which Mr Obama did well.
The claim has been questioned by the Obama campaign, which argues that Mrs Clinton's popular vote calculation includes disputed contests in Michigan and Florida, and does not include results from several caucus states in which Mr Obama did well.
Barack Obama claims election milestone
Mr Obama hopes his pledged delegate majority will encourage the remaining undecided super-delegates to back him.
Mr Obama hopes his pledged delegate majority will encourage the remaining undecided super-delegates to back him.
In Kentucky, Mrs Clinton won 65% of the vote to Mr Obama's 30%.
So far, he has won 1,940 of the 2,026 delegates he needs to clinch the nomination
Voters in Oregon, which has a mail-in voting system, had until 2000 local time (0300 GMT) to return their ballots to election offices.
BBC North America editor Justin Webb says Mr Obama wants to suggest without quite saying so that the primary season is closing and the general election race is beginning.
Mrs Clinton has warned Mr Obama against declaring premature victory, saying it would be a "slap in the face" to her millions of supporters so far and those states yet to vote.
Mrs Clinton has warned Mr Obama against declaring premature victory, saying it would be a "slap in the face" to her millions of supporters so far and those states yet to vote.
'Next challenge'
Racial attitudes
Mr Obama's aides are increasingly pushing the message that he has all but wrapped up the Democratic nomination and will be the one to face Mr McCain in November's general election.
In Kentucky, Mrs Clinton won 65% of the vote to Mr Obama's 30%.
In Oregon, with over half of the state's precincts reporting, Mr Obama was leading Mrs Clinton by 16 points.
Exit polls conducted by the Associated Press news agency suggested that Mrs Clinton's Kentucky victory was rooted in her strong support among the state's many white working class voters.
Hillary Clinton's victory speech in Kentucky
Hillary Clinton's victory speech in Kentucky
"As we near victory in one contest, the next challenge is already heating up," campaign manager David Plouffe wrote in an e-mail to supporters on Monday.
Three-quarters of white voters without a college education backed the New York senator, the poll suggested.
"President Bush and Senator McCain have begun co-ordinating their attacks on Barack Obama in an effort to extend their failed policies for a third term."
Racial attitudes may also have motivated some Kentucky voters' decisions: of the 20% of white voters who said that race a had played a part in their choice, nine out of ten backed Mrs Clinton.
BBC North America editor Justin Webb says Mr Obama wants to suggest without quite saying so that the primary season is closing and the general election race is beginning.
Phone surveys of Oregon voters painted a strikingly different picture of that state's electorate.
Our correspondent adds that although Mrs Clinton insists the race is still on, the truth is that the undecided super-delegates are moving steadily towards Mr Obama.
Mr Obama won 60% of the state's white voters, and even blue-collar white voters were evenly divided between the two candidates.
Mr McCain, senator for Arizona, has already begun targeting Mr Obama as his probable opponent in November.
Just 10% of the state's voters said that race was important when deciding their vote, and they were split evenly between Mr Obama and Mrs Clinton.
Monday saw him criticise Mr Obama over comments he made a day earlier suggesting that Iran does not pose the same level of threat to the US as the former Soviet Union once did.
As the results were coming in, Mr Obama, Mrs Clinton and Mr McCain revealed details of how much money they had raised in April.
In response, Mr Obama said that while Iran was a "grave threat", it had no nuclear weapons whereas the Soviet Union "had thousands".
Mr Obama raised $31m (£15.5m), less than he raised in March, but still the highest of the three presidential hopefuls.
Mrs Clinton's campaign took in $22m (£11.5m), its second best fundraising month so far in the campaign, while Mr McCain managed to raise $18m (£9m), his best ever monthly total.
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