Canada will not publicly set "red lines" that Iran must not cross if it wants to avoid a war over its nuclear program, rebuffing Israeli Prime Minister Benjamin Netanyahu's call to back him on issuing an ultimatum.

Prime Minister Stephen Harper met face to face with Mr. Netanyahu in New York on Friday morning, but it was a rare occasion when Mr. Harper did not offer the political support that his Israeli political ally wanted.

Mr. Harper avoided setting a "red line" of his own – and a senior Harper government official said Canada will not openly back a specific trigger for war to stop Iran from gaining nuclear weapons.

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"Canada will not be publicly setting red lines. That is for others to do," the official said. "We will continue to work with our allies to find a peaceful resolution on Iran."

Mr. Netanyahu has been in a public dispute with U.S. President Barack Obama over where to draw the line for Iran. Mr. Obama has said he won't let Iran obtain nuclear weapons, but Mr. Netanyahu insists Iran must know it will be attacked if it enriches enough uranium to make a bomb.

Mr. Harper was clearly not willing to get in the middle of Israel's disagreement with the United States, Canada's most important ally, on a major international-security issue.

On Thursday, Mr. Netanyahu had brought a cartoon-like drawing of a bomb to the United Nations to make his point, drawing a red line across it. At a brief photo op at the outset of their meeting, Mr. Netanyahu greeted Mr. Harper by voicing a similar message.

"I tried to say something yesterday that I think reverberates around the world – as you just told me – and that is to translate the agreement in principle of stopping Iran from developing nuclear weapons to practice," Mr. Netanyahu said. "That means setting red lines on their enrichment process, which is the only discernible and vulnerable part of their nuclear program."

Mr. Harper, however, did not express agreement – at least not in public.

"Our country has not been shy about warning the world about the danger that the Iranian regime ultimately presents to all of us," he told Mr. Netanyahu. "As you know, we want to see a peaceful resolution to all this."

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After the meeting, Mr. Netanyahu's spokesman, Mark Regev, refused to say whether Mr. Netanyahu had urged Mr. Harper to back his call for an early "red line" ultimatum. "I'm not going to speak about that level of detail in the meeting," Mr. Regev said.

Mr. Regev said Iran is getting the message about red lines from other countries in addition to Israel, and then praised Canada for cutting off diplomatic relations with Iran.

Mr. Harper did not take questions from reporters, so he did not detail his views on the issue. Any military strike on Iran would be led by either the U.S. or Israel, so Mr. Harper's government is now planning to leave the debate on the trigger-point up to them.

Mr. Netanyahu insists that Iran must know that it will be attacked if it enriches enough uranium to make one bomb. He argues that is a point that can be detected by other countries – and that Iran will back down if it faces a clear ultimatum.

The Obama administration argues that although Iran is now enriching uranium to 20-per-cent purity, it would still take time to further enrich it to higher bomb grade – and the U.S. would be able to detect it when Iranians try. Both they and the European nations involved in nuclear talks with Iran argue there is more time for diplomacy to prevent a war – a position Mr. Harper appears to be echoing.

Mr. Harper and his Israeli counterpart certainly agree on one step: that the world should adopt more sanctions to isolate Iran. Mr. Harper called for that action in a speech in New York Thursday, while noting he does not mean to advocate war.

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Mr. Regev, however, said while sanctions may have had an effect, they have not been successful thus far – and time is running out. By this time next year, Iran will have enough enriched uranium for a bomb, he said, and that's why all countries must back a clear ultimatum now.

"So it's important that we take action today – all of us – to prevent that from happening. That's the bottom line and that's why we need a red line."