Barack Obama will make a symbolic trip to Iowa on Tuesday, revisiting the state that launched his underdog bid for the White House on a day he hopes will put him over the top in the number of delegates needed to help clinch the nomination.

The planned Iowa rally, which the campaign announced on Saturday, will take place as polls close in Oregon and Kentucky in voting the Obama campaign believes will bring the Illinois senator a step closer to defeating his rival, New York Sen. Hillary Clinton.

Polls suggest Obama will win Oregon handily while Clinton is expected to prevail in Kentucky by a wide margin.

But the Obama campaign expects that when the results from both primary contests are added to his existing tally, he will have racked up more than half of the pledged delegates awarded in the state-by-state contests, making him the likely winner in the battle to become his party's nominee to face Republican John McCain in the November election.

"It will be (a) nice reunion with everybody who helped us get started," Obama told reporters during a stop at an amusement park outside Portland, speaking about the Iowa trip.

Obama said earlier this week his campaign would declare on Tuesday it had won the majority of pledged delegates.

Neither Obama nor Clinton will have enough pledged delegates to lock up the nomination, but Obama says superdelegates - party leaders and elected officials with their own vote in the process - should back the leader in pledged delegates.

The nominating contests began in January in Iowa, where Obama beat Clinton, a former first lady who was the national front-runner then and had an aura of inevitability.

Iowa has a history of being closely divided between Democrats and Republicans in the presidential race and is expected to be an important battleground state in November.

An Obama aide played down the idea that the Iowa trip would be a "victory celebration."

"This is meant to be a look to what's ahead," said the aide, who spoke on condition of anonymity. "Iowa is a key general election state," the aide said, noting it had gone for Republican President George W. Bush in 2004 and former Vice President Al Gore, the Democratic nominee in 2000.

'NOT READY FOR IT TO BE OVER'

Clinton has given no sign she plans to exit the race before the final voting contests on June 3 in Montana and South Dakota. Puerto Rico votes on June 1.

"There's some people who've been saying for months that this is over and every time they say it the voters come back and say, 'Oh no, it's not. We're not ready for it to be over,'" Clinton said while visiting a distillery in Loretto, Kentucky.

"You don't quit on people and you don't quit until you finish what you started," she said.

Clinton argues her strength in big states like Ohio and Pennsylvania that may be critical in a presidential election makes her the best candidate against McCain.

But for two straight days she found herself sidelined as Obama sparred with McCain and Bush after the president said in a speech in Israel on Thursday that some politicians would pursue the "false comfort of appeasement" by talking with militant groups such as Hamas and Hezbollah and with Iran.

Obama has said he would meet with Iranian President Mahmoud Ahmadinejad, but would not talk with Hamas because the Palestinian group is not a state and does not recognize Israel.

Bush did not mention Obama, but the Illinois senator accused the president and McCain of fear-mongering.

"Understand that George Bush had a policy of not talking to North Korea and not talking to Iran and over the last eight years, they are stronger as a consequence of George Bush's foreign policy," Obama said at a rally in Roseburg, Oregon, on Saturday.

McCain spokesman Tucker Bounds said in a statement: "Barack Obama's pledge to unconditionally bring Mahmoud Ahmadinejad to the world stage isn't 'new politics,' it's incredibly weak judgment."

McCain, an Arizona senator, had breakfast in New York with the city's mayor, Michael Bloomberg, a political independent who has been mentioned as a possible running mate for either McCain or Obama.

Asked what the two discussed, McCain spokeswoman Brooke Buchanan said only, "They had a lovely breakfast."

The campaign trail was roiled by news that Democratic Sen. Edward Kennedy was hospitalized after suffering a seizure at his Cape Cod vacation home. All three candidates expressed hopes for his speedy recovery.