The United States, in a policy shift, says it will play a full role in future big-power talks with Iran over its nuclear program. Diplomats of the five permanent U.N. Security Council member countries and Germany, the so-called P5+1, meeting in London Wednesday, invited Iran to join them in an upcoming discussion.

The Bush administration had generally refused to take part in meetings involving Iran on the nuclear issue, saying that Tehran had to first agree to end a uranium enrichment program U.S. officials believe is weapons-related.

But in a departure from that policy, the Obama administration says it will join in future big-power discussions with Tehran, hoping it will prompt the Iranians to be more forthcoming.

Senior diplomats of the five permanent Security Council member states and Germany, who met in London Wednesday, said they would ask European Union chief diplomat Javier Solana to invite Iran to a meeting soon to seek a diplomatic solution to the "critical" nuclear issue.

At a news briefing, State Department Acting Spokesman Robert Wood confirmed the United States will take part in that meeting, in keeping he said with the Obama administration's willingness to engage directly with Iran on the basis of mutual respect and mutual interests.

"What is different is that the U.S. will join P5+1 discussions with Iran from now on. The P5+1 has asked Dr. Javier Solana to extend an invitation to the Islamic Republic of Iran, to meet with representatives of the P5+1. If Iran accepts, we hope this will be the occasion to seriously engage Iran on how to break the logjam of recent years and work in a cooperative manner to resolve the outstanding international concerns about it nuclear program," he said.

The major powers presented Iran last July in Geneva with an updated offer of incentives for it to suspend its enrichment drive and return to negotiations over its nuclear program.

Senior U.S. diplomat William Burns, who was the U.S. delegate at Wednesday's London meeting, also took part in the Geneva session - though the Bush administration had framed his attendance as a one-time affair.

Iran, which maintains its nuclear program is entirely peaceful, has spurned the incentives and says it has a right to pursue an enrichment capability.

The development in the nuclear talks was somewhat overshadowed by word from Tehran that detained American journalist Roxana Sebari was being charged by Iranian authorities with espionage. The United States has been pressing, through Swiss interlocutors, for the release of Saberi, who has been detained in Iran since January.

At a photo session with Bulgaria's foreign minister Wednesday, Secretary of State Hillary Clinton expressed concern about the case. 

"We are deeply concerned by the news we are hearing. We have asked the Swiss, who as you know are our protectorate in Iran, to obtain the most accurate, up to date information. I will, as will the rest of the [State] Department, continue to follow this very closely. And, we wish for her speedy release and return to her family," she said.

Clinton had asked for Saberi's early release in a diplomatic note passed to Iranian officials at a conference on Afghanistan late last month at the Hague.

Spokesman Wood, under questioning, said the action against Saberi was not the response the administration has hoped for in its outreach to Iran. For direct diplomacy with Iran, he said, "we need a partner with an outstretched hand, as well."