WASHINGTON (Reuters) - President George W. Bush and his top policymakers misstated Saddam Hussein's links to terrorism and ignored doubts among intelligence agencies about Iraq's arms programs as they made a case for war, the Senate intelligence committee reported on Thursday.

The report shows an administration that "led the nation to war on false premises," said the committee's Democratic Chairman, Sen. John Rockefeller of West Virginia. Several Republicans on the committee protested its findings as a "partisan exercise."

The committee studied major speeches by Bush, Vice President Dick Cheney and other officials in advance of the U.S.-led invasion of Iraq in March 2003, and compared key assertions with intelligence available at the time.

Statements that Iraq had a partnership with al Qaeda were wrong and unsupported by intelligence, the report said.

It said that Bush's and Cheney's assertions that Saddam was prepared to arm terrorist groups with weapons of mass destruction for attacks on the United States contradicted available intelligence.

Such assertions had a strong resonance with a U.S. public, still reeling after al Qaeda's September 11, 2001, attacks on the United States. Polls showed that many Americans believed Iraq played a role in the attacks, even long after Bush acknowledged in September 2003 that there was no evidence Saddam was involved.

The report also said administration prewar statements on Iraq's weapons programs were backed up in most cases by available U.S. intelligence, but officials failed to reflect internal debate over those findings, which proved wrong.

PUBLIC CAMPAIGN

The long-delayed Senate study supported previous reports and findings that the administration's main cases for war -- that Iraq had weapons of mass destruction and was spreading them to terrorists -- were inaccurate and deeply flawed.

"The president and his advisors undertook a relentless public campaign in the aftermath of the (September 11) attacks to use the war against al Qaeda as a justification for overthrowing Saddam Hussein," Rockefeller said in written commentary on the report.

"Representing to the American people that the two had an operational partnership and posed a single, indistinguishable threat was fundamentally misleading and led the nation to war on false premises."

A statement to Congress by then-Defense Secretary Donald Rumsfeld that the Iraqi government hid weapons of mass destruction in facilities underground was not backed up by intelligence information, the report said. Democratic Sen. Ron Wyden of Oregon said Rumsfeld's comments should be investigated further, but he stopped short of urging a criminal probe.

The committee voted 10-5 to approve the report, with two Republican lawmakers supporting it. Sen. Christopher Bond of Missouri and three other Republican panel members denounced the study in an attached dissent.

"The committee finds itself once again consumed with political gamesmanship," the Republicans said. The effort to produce the report "has indeed resulted in a partisan exercise." They said, however, that the report demonstrated that Bush administration statements were backed by intelligence and "it was the intelligence that was faulty."

White House spokeswoman Dana Perino said: "We had the intelligence that we had, fully vetted, but it was wrong. We certainly regret that and we've taken measures to fix it."

PUBLIC SUPPORT

U.S. public opinion on the war, supportive at first, has soured, contributing to a dive in Bush's popularity.

The conflict is likely to be a key issue in the November presidential election between Republican John McCain, who supports the war, and Democrat Barack Obama, who opposed the war from the start and says he would aim to pull U.S. troops out within 16 months of taking office in January 2009.

Rockefeller has announced his support for Obama.

The administration's record in making its case for Iraq has also been cited by critics of Bush's get-tough policy on Iran. They accuse Bush of overstating the potential threat of Iran's nuclear program in order to justify the possible use of force.

A second report by the committee faulted the administration's handling of December 2001 Rome meetings between defense officials and Iranian informants, which dealt with the Iran issue. It said department officials failed to share intelligence from the meeting, which Rockefeller said demonstrated a "fundamental disdain" for other intelligence agencies.

(Additional reporting by Andy Sullivan, Donna Smith)