A suspected member of a pro- government militia (C) beats people at a rally of Mousavi supporters in Tehran, 15 Jun 2009

The Obama administration is ratcheting-up its expressions of concern about the situation in Iran, given new reports of government-inspired violence against election protesters.

But officials are also reiterating weekend comments by Vice President Joe Biden that the administration still aims to try direct diplomacy to persuade the Tehran government to cease its pursuit of a nuclear weapons capability and stop supporting terrorism.

State Department Spokesman Ian Kelly set the tone in a statement read at the daily briefing, saying the United States is closely watching the events unfolding in Iran and deeply troubled by reports of violence arrests and possible voting irregularities.

State Dept. Spokesman Ian Kelly points to a reporter at a press briefing in Washington (File)

"The enthusiasm and robust debate these elections engendered captured the attention of the world. And the essential right of people to express themselves peacefully needs to be respected," he noted. "The international community remains committed to seeing Iran living up to its international responsibilities, and we will continue to use all avenues to try to convince Iran to meet its international obligations," he said.

The spokesman defended the relatively mild language of the statement on the street violence in Tehran and elsewhere, but a senior official said later that if reports of gunfire and possible casualties at a pro-opposition rally in Tehran are confirmed, it would be something the United States would condemn outright.

Kelly made clear, as did the Vice President Biden on Sunday, the election trouble has not derailed the administration's stated commitment to try to engage Iran directly on the nuclear issue.

"This is a very serious issue, the issue of Iran acquiring nuclear weapons. As we go forward we are going to make our decisions based on U.S. national interests. And of course we are following the situation very closely. But as the Vice President said yesterday, we have made the decision to pursue direct diplomacy with Iran, particularly through the multi-lateral context," he said.

Kelly said Iranian authorities need to take vote-fraud charges seriously and look into them. But he stopped short of endorsing the announced decision of Iranian Supreme Leader Ayatollah Ali Khamenei to have the powerful Guardian Council of Islamic clerics investigate the allegations.

He said the international community's options are limited, given that the Tehran government banned international observers from the balloting.

On another issue, Kelly denied an Israeli press report that the State Department's envoy for Iran and the Gulf region, Dennis Ross, was being relieved of his duties, saying the veteran diplomat and policy analyst is not being fired or ousted, and enjoys the full confidence of Secretary of State Hillary Clinton.