U.S. President Barack Obama said on Tuesday he would like to see new UN sanctions placed on Iran in a matter of weeks as he and French President Nicolas Sarkozy presented a united front on Tehran's nuclear program.

Obama and Sarkozy, at a joint White House news conference, made clear they felt it was time to move ahead with tougher sanctions that their governments have been negotiating with China, Russia, Germany and Britain.

"My hope is that we are going to get this done this spring," Obama said. "I'm interested in seeing that regime in place in weeks."

China, reluctant for months, is believed to be slowly falling in line in backing the idea of new sanctions.

Sarkozy said "the time has come to take decisions" on Iran and that with German Chancellor Angela Merkel and British Prime Minister Gordon Brown, "we will make all necessary efforts to make sure that Europe as a whole engages in the sanctions regime."

The United States and its allies believe Iran is seeking to develop a nuclear weapon, a charge Tehran denies.

Obama said the long-term consequences of a nuclear-armed Iran are unacceptable and that Tehran had so far rejected diplomatic entreaties.

"The door remains open if the Iranians choose to walk through it," he said.

G8 says nuclear Iran 'unacceptable'

Also on Tuesday, the United States failed to win overwhelming support from world economic powers for sanctions to block Tehran's nuclear ambitions as G8 foreign ministers issued an insipid statement on Iran.

In a joint statement issued after the meeting of the leading industrialized nations in Ottawa, Canada, foreign ministers of the Group of Eight countries said that an Iran with nuclear weapons is unacceptable.

"Ministers agreed to remain open to dialogue and also reaffirmed the need to take appropriate and strong steps to demonstrate international resolve to uphold the international nuclear nonproliferation regime," the communique said.

Russia, which has shown reluctance to back the American push for a fourth round of UN sanctions, reportedly refused to bow to U.S. pressure for a tougher diplomatic stance against Tehran.

Earlier, U.S. Secretary of State Hillary Clinton, launching the G8 summit Monday, said the world could not accept a nuclear-armed Iran and that China could help resolve the impasse with Tehran.

Ahead of the meeting, Clinton seemed focused not on Russia but China, playing down fears that the eastern power was out of step with the other veto-wielding members of the UN Security Council on Iran.

"China is part of the consultative group that has been unified all along the way, which has made it very clear that a nuclear-armed Iran is not acceptable to the international community," Clinton told CTV in an interview.

Despite the setback over Russian support, Clinton remained upbeat about the prospect of a consensus after the meeting closed.

Sanctions were a part of diplomacy, she said, adding that Iran had repeatedly shown an unwillingness to fulfill its international obligations over the last 15 months.

"That's the basis on which I express my optimism that we're going to have a consensus reached in the Security Council," she told reporters.

The two-day meeting brought together foreign ministers from the Group of Eight industrialized countries, which includes the United States, Canada, Britain, France, Japan, Germany, Italy and Russia.

Opening the conference earlier Tuesday, Canadian Prime Minister Stephen Harper said Iran must halt its nuclear enrichment activities and comply with international demands to come clean about its atomic program.

On behalf of the ministers, Harper urged the world to adopt a heightened focus on the Iranian nuclear issue and take stronger coordinated action against Iran.

But China, which has close economic links to Iran, has repeatedly said that the world needs more time to find a diplomatic solution to the standoff over the Iranian nuclear program, which Tehran insists is purely for peaceful purposes.

U.S. officials have indicated that while the countries at this week's G8 conference are largely agreed on the likelihood of new sanctions against Iran, the scope and severity of the new measures remained to be worked out.

Those discussions have gathered steam since Tehran rejected an offer of a nuclear fuel swap deal that would have been brokered by the International Atomic Energy Agency (IAEA).

U.S. Deputy Secretary of State James Steinberg, speaking to reporters in Washington, said the United States was encouraged by some of the signs coming from Beijing.

"On issues of concern to us, we have seen some progress," Steinberg said.

Turkish backing?

Earlier Monday, Turkish Prime Minister Tayyip Erdogan said he did not favor imposing economic sanctions to pressure Iran into showing that it has no covert nuclear weapons program.

Erdogan discussed different approaches with visiting German Chancellor Angela Merkel to international efforts to rein in Iran's nuclear ambitions, but made clear Turkey's reluctance to back the use of sanctions.

"We are of the view that sanctions are not a healthy path and that the best route is diplomacy," he said at a joint news conference with Merkel.

Turkey is a non-permanent member of the United Nations Security Council and Erdogan said it had not yet reached a firm decision on how it would vote on a U.S.-backed sanctions resolution.

Merkel urged NATO ally Ankara to be ready to support the imposition of sanctions through the UN unless Iran shows transparency to assure the international community that it has no ambitions for nuclear weapons.

"We would be happy if Turkey votes in April on the Iran issue together with the United States and the European Union," she said.

Turkey, frustrated by the slow progress of its EU membership negotiations, doubts the effectiveness of sanctions and its trade would inevitably suffer if sanctions were imposed on its fellow Muslim neighbor.

"Turkey shares a 380 km (240 mile) border with Iran and it is an important partner, especially in energy. When appraising our relations we shouldn't ignore this," Erdogan said.

He also raised doubts about the results of three earlier rounds of milder sanctions against Iran.

In an apparently veiled reference to Israel, the Turkish leader referred to another country in the region that possessed nuclear weapons. Israel is widely assumed to have the bomb but has never admitted to possessing nuclear weapons.

"We are against nuclear weapons in our region. But is there another country in our region that has nuclear weapons? Yes, there is. And have they been subjected to sanctions? No," Erdogan said.

Turkey is worried about the potential for a nuclear arms race in the region between Iran and Israel, though it does not feel directly threatened by either country.

"If the world trusts us, we would fine a middle path with Iran. I hope that we will reach a result if we continue to work," Erdogan said.

Despite good relations with Tehran, Erdogan's own attempts to persuade the Iranian leadership to make moves needed to allay international concerns have so far come to naught.