US President Barack Obama has renewed his administration's offer of dialogue and diplomacy with Iran.
Mr Obama addressed Iranians in a new videotaped appeal to mark the observance of Nowruz, which is an ancient festival celebrating the arrival of spring.
A year after his offer of a new beginning with Iran failed to achieve concrete results, Mr Obama also pledged to pursue aggressive sanctions to prevent Iran from getting a nuclear weapon.
He said: 'We are working with the international community to hold the Iranian government accountable because they refuse to live up to their international obligations.
'But our offer of comprehensive diplomatic contacts and dialogue stands.'
Iran, which has refused to halt its uranium enrichment program, denies it is seeking to build a nuclear bomb and says its nuclear programme is aimed at generating electricity.
Mr Obama said Washington was committed to a 'more hopeful' future for the Iranian people despite US differences with Iran's government.
During his first year in office, Mr Obama marked Nowruz with a then-unprecedented message offering Iran a 'new beginning' of diplomatic engagement with the US.
However, Iran rebuffed Mr Obama's gesture and relations soured further when Iranian authorities cracked down on opposition protestors after a disputed election last June, drawing US condemnation.
Mr Obama said: 'Over the course of the last year, it is the Iranian government that has chosen to isolate itself, and to choose a self-defeating focus on the past over a commitment to build a better future.
'Even as we continue to have differences with the Iranian government, we will sustain our commitment to a more hopeful future for the Iranian people.'
The US is anxious not to undermine growing domestic opposition to President Mahmoud Ahmadinejad's government and has emphasised that any sanctions will be aimed at Iran's government, not its people.
'I want the Iranian people to know what my country stands for. The United States believes in the dignity of every human being, and an international order that bends the arc of history in the direction of justice,' Mr Obama said.
He said the US wanted 'a future where Iranians can exercise their rights, to participate fully in the global economy, and enrich the world through educational and cultural exchanges beyond Iran's borders. That is the future that we seek. That is what America is for.'
