But even as Washington tellingly praised London, not Tehran, for the end of the tense standoff over the detained sailors and marines, Iran flatly rejected UN demands to suspend uranium and reprocessing activities.

US President George W. Bush, on his Texas ranch for a long Easter weekend, spoke for about an hour by secure video with British Prime Minister Tony Blair, US national security council spokesman Gordon Johndroe told reporters.

"The president welcomed the safe return of the British personnel who had been detained in Iran. He also commended the British on their resolve in bringing the situation to a peaceful resolution," said Johndroe.

The Britons were seized in the northern Gulf on March 23, with Iran alleging they were in Iranian waters -- a charge denied by London.

US State Department spokesman Sean McCormack accused Iran of using "hostage-taking as a tool of its international diplomacy," and confirmed that Washington had toned down its rhetoric throughout the standoff.

"In the context of an ongoing hostage crisis, of course we are not going to say anything that could make the situation worse or make it more difficult to realize a peaceful solution," he said. "Absolutely, we're going to tailor our rhetoric."

At the same time, McCormack hinted at possible face-to-face talks between US Secretary of State Condoleezza Rice and Iranian Foreign Minister Manouchehr Mottaki on the sidelines of an international conference on Iraq in early May.

"We have said from the beginning, when this first surfaced, that if there would be a ministerial conference, that we are not going to exclude any particular diplomatic interaction," he said.

McCormack emphasized the possible bilateral meeting would focus on Iraq exclusively, and not address the Iranian nuclear program. US officials denied any link to the Britons' release.

Johndroe made clear that the release of the seven British marines and eight sailors would not ease international pressure on Iran to suspend key nuclear activities, and hinted at possible new sanctions.

"I would view the detention of the British sailors as not in line with their willingness to work with the international community," said Johndroe, referring to Iran's leaders.

"What would show that they are more in line with the international community is to comply with the UN Security Council resolutions, and suspend their uranium enrichment and reprocessing activities," said Johndroe.

"We'd be hopeful to not have to go back to the UN Security Council for an additional sanction regime," the spokesman said.

Shortly after he spoke, Iranian state television reported that Iran's nuclear chief Ali Larijani told the European Union there was no chance that Tehran would suspend uranium enrichment.

The United States has accused Iran of using its civilian nuclear program as cover for efforts to develop a nuclear arsenal. Tehran denies the charge.

On another front, US Defense Secretary Robert Gates said Thursday that US officials were not inclined to release five Iranians captured in Iraq, and accused Iran of supporting Iraqi insurgents.

"I think there's no inclination right now to let them go," Gates told reporters, when asked about the fate of the five Iranians held since January.

Gates rejected speculation that the United States was preparing to release the group or allow consular access to them as part of a deal involving Iran's release of the British captives.

And controversial former US ambassador to the United Nations John Bolton described the end of the hostage standoff as a "double victory" for Tehran.

Iran "won a victory when they captured the hostages and they won a victory when they released the hostages" said Bolton, interviewed on the US-funded Alhurra Arabic-language television network.

"I think they were testing British resolve in response to this provocative act and I think they already had their answer, which was that the British are not going to respond in a strong fashion," he said.

Bolton left the UN post in January. He will be replaced by the former US ambassador to Iraq, Zalmay Khalilzad.

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