U.S. Senator Barack Obama is spending his first full day as the presumptive Democratic presidential nominee giving a major foreign policy speech, addressing a powerful American labor union, attending a high-powered fundraising event, and doing interviews for American television networks.   His rival, Senator Hillary Clinton, has remained visible, but tightlipped as to when she will concede and throw her support behind Obama. VOA's Michael Bowman reports from Washington.

Barack Obama waves prior to addressing the American Israel Public Affairs Committee (AIPAC) Policy Conference 2008, 4 June 2008

Congratulations and further endorsements poured in for Barack Obama Wednesday, including acknowledgments from some Republican quarters. The White House says President Bush congratulates Obama for his "historic achievement" that "reflects the fact that the country has come a long way."

Hours after becoming the first person of color to clinch the presidential nomination of a major U.S. political party, Obama addressed a Washington gathering of the American Israel Public Affairs Committee (AIPAC). There, he pledged an unyielding commitment to Israel's security, spoke of the need for peace in the Middle East, and clarified previous comments about his willingness, as president, to one day meet face-to-face with the leaders of Iran.

He also paid tribute to fellow-Democratic contender Hillary Clinton, who vied to become America's first woman president.

"I want to publicly acknowledge Hillary Clinton for the outstanding race that she has run," he said.  "She is a true friend of Israel. She is a great Senator from New York. She is an extraordinary leader of the Democratic Party, and she has made history alongside me over the last 16 months. So I am very proud to have competed against her."

Hillary Rodham Clinton speaks to the American Israel Public Affairs Committee (AIPAC), 4 June 2008

Clinton has yet to officially drop out of the presidential race, although she has told supporters that she would be open to serving as Obama's vice presidential running mate. Short of a formal concession, however, Clinton has signaled that she is aware of Obama's status as presumptive presidential nominee.  The senator also spoke at AIPAC, moments after Obama left the stage.

"The Democratic Party's strong commitment to the state of Israel is one of our party's most-cherished values," she noted.  "And it will continue under the next Democratic president. I know [that] Senator Obama understands what is at stake here. It has been an honor to contest these primaries with him.  And let me be very clear: I know that Senator Obama will be a good friend to Israel."

In a telephone call early Wednesday, Obama and Clinton agreed to meet face-to-face, but discussed no specifics. Just how and when Clinton exits the race - and what, if any, concessions she may want from Obama in doing so - will be closely watched as Democratic officials work to rebuild party unity after an often-bruising primary campaign season.

Sen. John McCain speaks to supporters during a town hall meeting campaign event in Baton Rouge, Louisiana, 4 June 2008

On the Republican side, Arizona Senator John McCain continued to question Obama's message of bringing change to Washington. Speaking in Louisiana, the presumptive Republican presidential nominee called for an expanded debate schedule between him and Obama that would include weekly joint town hall meetings across the country leading up to the November election.

"Joint town halls would show we both understand that this election could not be more important to the future security and prosperity of American families," he said.  "It is, indeed, a 'change' election. No matter who wins this election, the direction of the country is going to change dramatically. But the choice before the American people is between the right change and the wrong change."

An Obama spokesman calls the joint town hall proposal "appealing."

Barack Obama, 46, is vying to become one of America's youngest presidents. His age contrasts sharply with that of John McCain, 71, would become one of the oldest to enter the Oval Office.