MONTREAL — Prime Minister Stephen Harper's reaction to the death of a Canadian peacekeeper in Lebanon was irresponsible and risks making Canada irrelevant in the region, interim Liberal leader Bill Graham said Thursday.

"Everybody watching Canada at this time is concerned about whether or not Canada is, by its actions, making itself irrelevant in terms of being able to contribute to the possibility of a long-term peace in the Middle East,'' Graham said.

The former Liberal foreign affairs and defence minister said Harper has signalled a shift in Canadian policy by strongly backing Israel in the conflict.

In the wake of the presumed death of Maj. Paeta Hess-von Kruedener of Kingston, Ont., Harper questioned why the UN remained in the lookout post along the Israeli-Lebanese border two weeks after Israel's military offensive began.

"I found Mr. Harper's reaction...completely unacceptable,'' Graham said after a meeting with an environmental group.

Canada has been sending peacekeepers to the Middle East since former Liberal prime minister Lester B. Pearson first sent them there in the 1960s, Graham said.

The Canadian peacekeeper died Tuesday along with three other unarmed observers at a clearly marked UN post.

"Mr. Harper showed irresponsibility by putting into question Canada's traditional position contributing to peace,'' Graham said.

While noting that Israel has the right to defend itself against a terrorist organization like Hezbollah, which the Liberals previously banned in Canada, Graham said Canada has always stressed long-term peace rather than an immediate military solution.

He said Canada must retain its independence in the face of views from the United States and others.

"Harper shouldn't simply repeat what (U.S. President George W.) Bush or (Secretary of State Condoleezza) Rice have said.''

UN Secretary General Kofi Annan said Tuesday the Israeli attack on the UN post appeared to be deliberate. Harper responded that the facts suggested otherwise, noting the Jewish state has co-operated with Canada over the evacuation of its citizens from Lebanon.

Graham didn't address the pertinence of the presence of the observation post. But he recalled that the Israelis invited the UN to watch the Hezbollah, which controls the area.

He expressed confidence in the Israeli investigation of the fatal incident.

"Israel has a judicial system without equal in the world, and I have confidence that an inquiry can establish the facts.''

Graham said it's too early to say if Canadian soldiers should participate in a peacekeeping operation in the region.

"It's impossible to respond to this question without knowing the circumstances,'' he said.

"The soldiers could be useful if there exists conditions for peace. Sending Canadian military to a war zone doesn't contribute to a solution.''