President Bush batted away questions about the CIA leak investigation Friday, unable at an Americas summit thousands of miles from Washington to escape the controversy that has ensnared a top White House official and weakened his own popularity.

Taking questions for the first time since the indictment of I. Lewis "Scooter" Libby (search), Vice President Dick Cheney's former chief of staff, Bush declined to answer calls from Democrats and some Republicans that he apologize for any administration official's involvement in the case.

Bush also wouldn't say if staff changes were in the works. He sidestepped a question about whether Karl Rove (search), his top political adviser who remains under investigation in the CIA leak case, should stay on the job. And the president wouldn't comment on whether Rove told him the truth about his role in the events that led up the investigation.

"You're trying to get me to comment on the investigation, which I'm not going to do," Bush told a small group of reporters after meeting with Latin American leaders on the sidelines of the 34-nation Summit of the Americas. "And I hope you understand that. It's a serious investigation, and it's an important investigation. But it's not yet over."

The questions about the outing of CIA officer Valerie Plame (search) shadowed Bush as he attended the two-day summit here which ends Saturday. Bush goes on to stops in Brazil and Panama.

Back in Washington, Democratic National Committee Chairman Howard Dean has called on Bush to hold a prime-time news conference to answer lingering questions.

Libby's indictment has enabled Democrats to raise anew questions about the Bush administration's primary justification for invading Iraq, the assertion — later proven wrong — that Saddam Hussein had weapons of mass destruction (search).

Senate Minority Leader Harry Reid and other Democrats have called on Bush to apologize for the White House misleading the public on the CIA leak case. Privately, some Republicans have urged the same.

In June 2004, Bush said he stood by his previous pledge to "fire anybody" in his administration shown to have leaked Plame's name. His press secretary, after checking with Libby and Rove, assured the public that neither man had anything to do with the leak.

It turns out both were involved, though Rove has not been charged and neither man has been accused of breaking the law against revealing the identity of an undercover agent.

Libby was charged with lying to investigators and the grand jury about leaking the CIA status of Plame, who was a covert officer. Plame's CIA status was exposed after her husband, former U.S. Ambassador Joseph Wilson (search), accused the administration of twisting intelligence before the war to exaggerate the Iraqi threat from weapons of mass destruction.

Special Counsel Patrick Fitzgerald is said to be still considering whether Rove illegally misled investigators.

The case has further damaged Bush's standing in the polls. A new AP-Ipsos poll found Bush's approval rating was at 37 percent, compared with 39 percent a month ago. A Washington Post-ABC News poll also found six in 10 Americans say Rove should resign.

Bush lamented being repeatedly asked in recent weeks about poll numbers that are the lowest of his presidency. To virtually every question on the leak case, he responded by pivoting to the importance of focusing instead on his agenda.

"I understand there is a preoccupation by the polls and by some," Bush said. "The way you earn credibility with the American people is to declare an agenda that everybody can understand, an agenda that relates to their lives, and get the job done."

Three Democratic congressmen have asked Cheney to testify on Capitol Hill about the disclosure of Plame's identity.

The Democratic Party, meanwhile, is seeking to capitalize on Bush's troubles to help elect members of their party to Congress in 2006. A fund-raising letter sent Friday by Democrat Nancy Pelosi alleged that "the Republicans have run this country under the mantle of profit, partisanship, and power for long enough."

The only question in the 12-minute exchange with reporters that Bush directly answered was one about how he would greet Hugo Chavez (search), the outspoken, leftist leader of Venezuela who is using the summit as a stage to needle Bush and bolster his own standing among Latin American nations. Bush promised to "of course, be polite."