"The view at the moment is that we are reluctant to initiate a high-level diplomatic dialogue with Iran until there has been some progress on this nuclear issue," Negroponte told the Senate Foreign Relations Committee during a hearing on his nomination.

Negroponte, who would become Secretary of State Condoleezza Rice's deputy, noted that Washington has had indirect dialogue with Iran through talks with European countries also concerned with Tehran's nuclear ambitions.

"We have been discussing the Iran issue with our European friends and the UN Security Council. And in the context of the nuclear issue there has been a dialogue with Iran, albeit indirectly," he said.

He said Washington was not warm to the idea of holding a regional conference on Iran, but did not rule out the possibility.

"I would not say that, as a matter of priority, one would have to go right to a regional-type conference or regional-type diplomatic scenario, although I don't think that that should be ruled out," he said.

UN Security Council resolution passed on December 23 imposed sanctions on Iran until it suspends uranium enrichment, which makes fuel for civilian nuclear reactors but also produces material for atomic bombs.

But Iran continues to defy the international community and has vowed to increase its enrichment capacity by installing 3,000 centrifuges, arguing that its nuclear program is strictly for civilian energy purposes.

On Iran and Syria's influence in Iraq, Negroponte said, "I believe that both ... have not been doing what they could do to support a peaceful course of events in Iraq. And I think that they know what they need to do."

The United States has accused Iran of interfering in Iraq and Syria of allowing foreign fighters to cross their border into Iraq. It has turned down advice to start a dialogue with either nation.

Iran and Syria, said Negroponte, "know what they need to do" to improve their relations with Washington, adding that he "would never want to say never with respect to initiating a high-level dialogue with either of these two countries, but that's the position, as I understand it, at this time."

Negroponte, currently the top US spy chief, would fill a post that has been vacant for several months since Robert Zoellick resigned last year. After the committee votes on his nomination, the full Senate will have to approve it.

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