OTTAWA – President Bush tried yesterday to repair America-Canada relations strained by years of bickering over trade and Iraq, although he stood by policies that have irritated Canadians.

He did promise Prime Minister Martin to work toward easing an American ban on Canadian beef.

Even as thousands of Canadians thronged the streets to protest his visit, Mr. Bush brushed aside suggestions that his decisions had damaged ties between America and Canada. Asked about polls that show Canadian opposition to his policies runs high, Mr. Bush pointed to his own re-election this month as the survey that mattered.

“We just had a poll in our country when people decided that the foreign policy of the Bush administration ought to stay in place for four more years,” Mr. Bush said at a joint news conference with Mr. Martin.

“I made some decisions, obviously, that some in Canada didn’t agree with, like, for example, removing Saddam Hussein and enforcing the demands of the United Nations Security Council,” Mr. Bush said.

While he acknowledged no mistakes, Mr. Bush joked about his reception here.

“I want to thank the Canadian people who came out to wave, with all five fingers, for their hospitality,” he said.

Indeed, Canadians for the most part lived up to their reputation for reserve as Mr. Bush made his way from the airport to downtown Ottawa. Most stood waving excitedly at Mr. Bush’s enormous motorcade as it snaked down the road.

Many of Mr. Bush’s opponents were polite. One of the first signs he saw read “Please Leave.” Others were more blunt. At lunchtime, a sign close to Mr. Bush’s motorcade urged him to go home and depicted him riding atop a missile with a swastika on it.

Twelve protesters were arrested after they clashed with riot police, officers said. One police officer was reported injured.

The beef ban is a leading irritant in a relationship that has suffered during Mr. Bush’s presidency, and the issue loomed large in Mr. Bush’s first official trip to Canada.

In their private meetings, Mr. Martin vented “a great deal of frustration that the issue hadn’t been resolved yet,” Mr. Bush said.

“This has been studied to death,” an exasperated Mr. Martin said of the Canadian beef ban, in place since May 2003.

The Bush administration has since opened its border to some Canadian beef, but live cattle remain prohibited. Canadian ranchers are desperate, estimating they have lost more than $2 billion.

“I believe that, as quickly as possible, young cows ought to be allowed to go across our border,” Mr. Bush said. But, he said, “There’s a bureaucracy involved. I readily concede we’ve got one.”

The latest study rests with the White House’s own Office of Management and Budget, and Mr. Bush said he had ordered the OMB to “expedite that (process) as quickly as possible.”

Yet a resolution is months off. OMB has three months to study a rule that would allow into America boxed beef and live cattle younger than 30 months; the deadline for completion of the study is mid-February. Then Congress has two months to scrutinize the proposed rule, a senior administration official said.

Mr. Bush had a cool relationship with Mr. Martin’s predecessor, Prime Minister Chretien, and the president canceled an official visit to Canada’s capital in May 2003 after their disagreement over the Iraq invasion broke out into public view.

The trip to Ottawa opened a broader reconciliation tour he plans to continue in Europe early next year.

Mr. Martin, who has been in office less than a year, has sought to repair the damage. Mr. Bush embraced the opportunity for a fresh start with Canada and its 32 million people.

The two leaders emphasized areas of agreement and cooperation, papering over their countries’ contentious history about the Iraq war.

Canada has pledged more than $200 million in humanitarian aid and reconstruction money and has agreed to forgive more than $450 million in Iraqi debt, Mr. Bush said. Canadian officials said the two leaders discussed what role the country might play in Iraqi elections two months off. Canada is experienced in monitoring elections.

At a time when Canada is debating whether to participate in the new American continental missile defense program, Mr. Bush told Mr. Martin the shield would protect much of North America, a senior Bush official said.