Canada's opposition parties are demanding that Prime Minister Stephen Harper reconsider his pro-Israeli remarks, warning that Ottawa's strong support of Israel's actions against Hezbollah could damage Canada's credibility as a future peacemaker in the region.

"We strongly urge the prime minister to reconsider some of his rhetoric and his language," interim Liberal Leader Bill Graham said in Vancouver on Tuesday.

Harper sided firmly with Israel since it began military air strikes against the Lebanese-based Hezbollah militant organization seven days ago.

He has called Israel's response "measured," saying the Jewish state had a right to defend itself. He called on Hezbollah and the Palestinian militant group Hamas to release Israeli prisoners and recognize Israel's right to exist.

Harper's public support for one side was a change to traditional Canadian foreign policy and would make it difficult for Canada to play the role of an international peace broker, both Graham and New Democratic Party (NDP) leader Jack Layton pointed out.

It was a Canadian tradition to work in the Middle East for long-term peace by being able to work with all sides of the conflict. Canada had to retain credibility among all sides in the region if it was to participate in a future stabilization force, Graham said.

"Canadians want their government to offer a balanced response to the crisis. Canadians want us to help everyone in the region come together," he said.

Harper has also voiced opposition to UN Secretary General Kofi Annan and British Prime Minister Tony Blair's call for an international security force in the Israel-Lebanon border, saying it was too early to send in such a force.

NDP leader Layton dismissed Harper's position, saying Canada should call for an immediate ceasefire and quickly commit to a role in a future peacekeeping force.

Harper's statement had "changed Canada's role as a neutral country," said Layton at a news conference on Tuesday in Ottawa.