(Corrects this Nov. 14 to clarify details of Bolton's recess appointment, paragraph 8.)

By Warren Strobel and John Walcott

WASHINGTON (Reuters) - Despite his professed opposition to the 2003 U.S. invasion of Iraq, President-elect Donald Trump is considering several of the major advocates of that war for top national security posts in his administration, according to Republican officials.

Among those who could find places on Trump's team are former top State Department official John Bolton and ex-CIA Director James Woolsey. Both men championed the Iraq invasion, which many analysts have called one of the major U.S. foreign policy debacles of modern times.

Also involved in transition planning for Trump's presidency is Frederick Fleitz, a top aide to Bolton who earlier worked at the CIA unit that validated much of the flawed intelligence on Iraq's weapons of mass destruction programs.

Although it is impossible to predict how a Trump foreign policy might evolve, one U.S. official who has served in Iraq said advocates of the 2003 invasion might be more inclined to commit additional U.S. forces to the fight against Islamic State there, despite the absence of a status of forces agreement that protects Americans from Iraqi legal action.

Paul Pillar, the top U.S. intelligence official for the Near East from 2000 to 2005, said that because Trump had little foreign policy experience and had given conflicting accounts of what policies he would pursue, the Republican president-elect's senior personnel appointments would be crucial.

"What we're seeing going on - and we should be worried about it - is a new president who on so many foreign policy issues has been all over the map," said Pillar, now at Georgetown University. "Thus, the senior appointments game that we go through every four years has more consequences than it usually does."

Bolton, who is under consideration as Trump's secretary of state, the officials said, and Woolsey, reported to be in the running for U.S. director of national intelligence, did not respond to requests for comment. The Trump transition team also did not immediately respond when asked for comment.Even if Bolton is nominated, Senate confirmation is not a foregone conclusion. In 2005, Senate Democrats - with the support of a single Republican – blocked a vote to confirm him as U.S. ambassador to the United Nations. He was appointed to that post by Republican President George W. Bush while the Senate was in recess.

NEOCONSERVATIVE REVIVAL?

Fleitz, in a brief phone conversation, confirmed he was involved in Trump's transition effort, but declined further comment.

A return to power for the three officials would represent a change of fortune for them and other "neoconservatives" who provided the intellectual backing for the invasion of Iraq. During the presidential campaign, some leading neoconservatives and Republican foreign policy veterans opposed Trump, saying he was unfit to lead.

The group saw its clout wane in Bush's second term, as U.S. troops in Iraq found themselves mired in a sectarian civil war, and has watched from the sidelines during Democratic President Barack Obama's eight years in power.

Trump, who takes office on Jan. 20, has said he opposed the invasion of Iraq, in which more than 4,000 U.S. troops and hundreds of thousands of Iraqis died, and which led to the creation of al Qaeda in Iraq, the forerunner to the violent, ultra-hardline Islamic State group.

Iraqi dictator Saddam Hussein's weapons of mass destruction and ties to al Qaeda, used to justify the invasion, proved to be nonexistent.

"As you know, for years I've been saying: 'Don't go into Iraq.' They went into Iraq. They destabilized the Middle East. It was a big mistake," Trump said in August 2015 on NBC's "Meet the Press" program.

His account that he always opposed the war was challenged during the campaign by Democratic rival Hillary Clinton, who cited a 2002 interview Trump gave to radio host Howard Stern in which he replied: "Yeah I guess so" when asked if he supported invading Iraq.

Consideration of Bolton, Woolsey and others is "another demonstration of how those who supported one of the biggest mistakes in American foreign policy have not been - they don't seem to be sufficiently discredited to be removed from the Washington foreign policy dialogue," Pillar said.

(Additional reporting by Mark Hosenball, Arshad Mohammed, Jonathan Landay and Doina Chiacu; editing by Yara Bayoumy and Peter Cooney)