International pressure is building on Tehran to halt its nuclear enrichment program, which Western nations say is aimed at developing the ability to build atomic weapons. Iran denies this, saying it needs nuclear energy to generate electricity.

Canadian Foreign Minister Lawrence Cannon said Iran would be "of critical concern" when G8 foreign ministers met in the Quebec town of Gatineau, across the river from the federal capital, Ottawa.

"I will discuss with my G8 colleagues what we can do to put additional pressure on Iran to persuade it to stop its nuclear enrichment activities," he told reporters on Friday.

"Unfortunately I believe we are left with little choice but to pursue additional sanctions against Iran, ideally through the United Nations Security Council." The United States wants the council to impose a fourth round of sanctions against Iran but needs the agreement of China, which for months refused to discuss the idea.

"We are seeking a strong resolution with sanctions that have the appropriate bite," State Department spokesman P.J. Crowley said on Friday.

A senior Chinese official took part in a conference call with five other world powers last week to discuss more sanctions but no deal emerged. China, along with Russia, has close business ties with Iran.

Cannon said the G8 would also discuss North Korea, which is boycotting international talks designed to end Pyongyang's efforts to build nuclear weapons.

The United Nations imposed new sanctions last year after North Korea detonated a device in May.

"I do think the sanctions are effective ... we will continue to enforce these sanctions aggressively until North Korea changes its course," said Crowley.

The G8 foreign ministers will start their meeting at 6 p.m. (2200 GMT) on Monday.

They are due to end at around 2 p.m. on Tuesday.