Washington - Senior Democratic Sen. Robert Byrd accused the Bush administration yesterday of exploiting fears over the Sept. 11 terrorist attacks to win support for an unprovoked war against Iraq and divert attention from dangers posed by al-Qaida.

In a broad condemnation of administration policies toward Iraq and terrorism, the West Virginian said that while the war toppled "a brutal, despicable despot," it has failed to improve life for Iraqis and left the United States more vulnerable to terrorists.

"Instead of damaging the terrorists, we have given them new fuel for their fury," he said.

Among the most outspoken critics of the Iraq war, Byrd delivered his remarks as the Senate debated a bill to authorize $400.5 billion in defense programs, a measure that would lift a 10-year-old ban on the study and production of low-yield nuclear weapons.

Democrats warned that the nuclear language could spark nuclear proliferation and represented a reckless policy. They lost two key votes yesterday and Tuesday to retain the ban on research and development of the "mini nukes" and another to allow study of the weapons while blocking their later development. The Senate instead adopted an amendment that would require the administration to get congressional authorization before developing such weapons.

Defense Secretary Donald Rumsfeld said the provision is needed to study the weapons at a time when terrorist states are increasingly developing weapons of mass destruction in underground facilities. "We have no plans to build or develop or manufacture or deploy or let alone use such a weapon," he said.

Byrd charged that the Bush administration invoked frightening images of "mushroom clouds" and "buried caches of germ warfare" to justify the Iraq war, adding: "It was the exploitation of fear."

The Bush administration has said the war liberated Iraq and ended Saddam Hussein's regime and will pave the way for democracy there and peace in the Mideast.

Byrd disagreed. He said that the war may have destabilized the Mideast and that the administration's warnings that Iraq harbored weapons of mass destruction have so far come up empty. "What has become painfully clear in the aftermath of war is that Iraq was no immediate threat to the U.S.," he said.

"It appears to this senator that the American people may have been lured into accepting the unprovoked invasion of a sovereign nation, in violation of long-standing international law, under false premises," Byrd said. "There is ample evidence that the horrific events of Sept. 11 have been carefully manipulated to switch public focus from Osama bin Laden and al-Qaida, who masterminded the Sept. 11 attacks, to Saddam Hussein, who did not."

He said the administration's claims raise "serious questions about prevarication and the reckless use of power."

Scott McClellan, a White House spokesman, dismissed Byrd's charges, saying, "It is widely known that Saddam Hussein had a weapons of mass destruction program." He said the United States has already determined Iraq had at least two mobile weapons labs.

He declined specific comments about the sweep of Byrd's Senate speech, which comes amid stepped-up criticism by Democrats of the war's aftermath.