US president Barack Obama strongly condemned Iran's crackdown on anti-government protesters and said on Tuesday the United States was 'appalled and outraged' by recent violence in the Tehran streets.

The United States would not interfere in the protests over Iran's contested election, and accusations it was instigating them were 'patently false and absurd,' Obama said as he opened his fourth news conference since taking office.

'I strongly condemn these unjust actions, and I join with the American people in mourning each and every innocent life that is lost,' he said.

'We must also bear witness to the courage and dignity of the Iranian people, and to a remarkable opening within Iranian society. And we deplore violence against innocent civilians anywhere that it takes place.'

The news conference followed heavy criticism from Republicans that Obama, a Democrat, has been too timid in backing the swelling street protests in Iran. Over the weekend, he sharpened his criticism of the Iranian government while trying to avoid the appearance of meddling.

Asked why it had taken him so long to express his outrage, Obama said the US approach had not been inconsistent.

'Ultimately the most important thing for the Iranian government to consider is legitimacy in the eyes of its own people,' he said, adding that it was crucial to make sure that his comments were not exploited by the Iranian government.

Obama said Tehran had a path to improve ties with the international community.

'We have provided a path whereby Iran can reach out to the international community, engage and become a part of international norms,' Obama said at a news conference. 'It is up to them to make a decision as to whether they choose that path.' 

He added that what has been seen recently has not been encouraging. 'It is not too late for the Iranian government to recognize that there is a peaceful path that will lead to stability and legitimacy and prosperity for the Iranian people - we hope they take it,' he added.-Reuters