The Senate voted Thursday to overturn the Bush administration's decision to allow Canadian cattle into the country nearly two years after they were banned because of mad cow disease (search).

The White House said President Bush would veto the measure if it ever reached his desk, warning that continuing to refuse Canadian beef would damage efforts to persuade other countries to buy U.S. beef.

Supporters fell short of the two-thirds majority needed to override a veto. The Senate's 52-46 vote was to reject the Agriculture Department's (search) decision to resume imports of Canadian cows under 30 months of age beginning next week. A similar measure has been introduced in the House, but leaders there have scheduled no vote on it.

"They've got mad cow disease," said Sen. Kent Conrad (search), D-N.D. "Now the question is, should we run the risk of opening our border to livestock imports from Canada, when the evidence demonstrates clearly they're not enforcing their regulations to reduce the risk to them and to us?"

Agriculture officials had planned to reopen the border next Monday. However, a federal judge on Wednesday granted a temporary injunction sought by Western ranchers seeking to keep the ban in place.

Western ranchers saw near-record cattle prices last year and want to protect those prices by refusing Canadian cattle.

U.S. meatpackers, however, say their inability to buy Canadian cattle has cost their industry more than $1.7 billion, forcing layoffs and idling production.

The United States banned cattle and beef shipments from Canada after mad cow disease turned up in an Alberta cow in May 2003.

Some imports of Canadian boneless beef are now shipped to the United States, but the border reopening would have expanded what is allowed.

The brain-wasting disease was confirmed in two more Alberta cows in January, and the lone U.S. cow to test positive for mad cow disease also came from Canada.

Senate debate centered on how negotiations with Japan and other countries would be affected by allowing Canadian cattle shipments. Japan, a market once worth $1.5 billion to U.S. beef producers, has not lifted the ban it imposed after the U.S. cow's infection was confirmed in 2003.

"Be careful what you ask for. We will take a giant step backward in our efforts to reopen markets to Japan, or for that matter, anywhere, if we vote today to approve this resolution," said Sen. Pat Roberts, R-Kan.

White House spokesman Scott McClellan said failure to reopen the border "would impede our efforts to reopen foreign markets to U.S. beef."

Foes of the border reopening said the opposite is true.

"Somehow you're going to give Japan confidence by allowing Canadian cattle to come into this country on the heels of four examples of mad cow disease in Canada? I don't think so," said Sen. Byron Dorgan, D-N.D.

Dorgan pointed out Americans bought about $75 billion more in Japanese goods than the United States sold to Japan last year.

Many lawmakers are calling for trade sanctions that would make it more difficult for the Japanese to sell their goods to the United States. Rep. Jerry Moran, R-Kan., and nearly three dozen other House members on Thursday introduced a measure calling for retaliation if Japan's beef ban continues.

"They stand to lose much more than the United States," Moran said.

The Agriculture Department had planned to allow Canadian cattle younger than 30 months of age and a wider array of meat from younger animals. The infection level is believed to rise with age.

Mad cow disease is the common name for bovine spongiform encephalopathy, or BSE. People who eat meat tainted with BSE can contract a degenerative, fatal brain disorder called variant Creutzfeldt-Jakob disease.