More than two-thirds of Americans believe the Bush administration has failed to make its case that a war against Iraq is justified, according to a poll by the Los Angeles Times published Tuesday.

Ninety percent of respondents said they don't doubt Iraq is developing weapons of mass destruction. But without new evidence from U.N. inspectors, 72 percent of respondents, including 60 percent of Republicans, said the president has not provided enough evidence to justify starting a war.

The Times poll, which interviewed 1,305 adults nationwide, was conducted from Thursday to Sunday, in the week after Iraq handed over its massive report on its arsenal to the United Nations. The margin of error was plus or minus 3 percentage points.

Support for a possible war appears to be weakening, with 58 percent saying they support a ground attack on Iraq, according to the poll. In an August Times poll, 64 percent said they would support a ground attack. In January, the Times and other polls found support for military action more than 70 percent.

Yet almost three-quarters of Americans support the way Bush is handling the threat of terrorism, and nearly three in five like how he's handling the country's affairs.

Sixty-three percent of those polled said war would be justified only if the United Nations finds a pattern of serious violations by Iraq. Only 22 percent agreed with the administration's position that any error or omission in Iraq's arms declaration is adequate to justify war; 6 percent said it would depend on the nature of the omissions; and 9 percent said they were not sure or declined to reply.

If U.N. inspections fail to find evidence of Iraqi weapons programs, almost half said they would oppose war. Only 41 percent would favor war, and 10 percent said they were undecided. Only 26 percent said they were willing to support war if the United States acted alone.

Respondents also believe war would have serious ramifications at home and abroad. Sixty-seven percent said war would likely increase the threat of terrorist attacks in the United States; 51 percent said they feel it would destabilize the Middle East; and 45 percent said it will adversely impact the U.S. economy.