U.S. President Barack Obama renewed his administration's offer of dialogue and diplomacy with Tehran late Friday, a year after his offer of a new beginning with Iran failed to achieve concrete results.

Obama, who addressed Iranians in a new videotaped appeal to mark Nowruz - an ancient festival celebrating the arrival of spring and the Persian New Year - has pledged previously to pursue aggressive sanctions to prevent Iran from getting a nuclear weapon.

"We are working with the international community to hold the Iranian government accountable because they refuse to live up to their international obligations," Obama said in the address released on Saturday, according to excerpts released by the White House.

"But our offer of comprehensive diplomatic contacts and dialogue stands," he said.

Iran denies Western claims it is seeking to build a nuclear bomb and says its nuclear program is aimed at generating electricity.

Later on Saturday, Ahmadinejad issued his own, more combative New Year's address to Iranians, in which he said that Iran would stand even more firmly against the West.

"Enemies have tried to weaken our country but they have failed and in the coming year we will stand even more firmly against them than before," he said.

Obama said Washington was committed to a "more hopeful" future for the Iranian people despite U.S. differences with Iran's government.

"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 - 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," Obama said in the video, which had Farsi subtitles.

Obama has signaled a willingness to speak directly with Iran about its nuclear program and hostility toward Israel, a key U.S. ally.

At his inauguration last year, the president said his administration would reach out to rival states, declaring "we will extend a hand if you are willing to unclench your fist."

Meanwhile, efforts to impose new sanctions on Iran have been slow to find unified support from U.S. allies.

"Our offer of comprehensive diplomatic contacts and dialogue stands," Obama said in the video. "Indeed, 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."

The United States has not had formal diplomatic relations with Iran since the 1979 Islamic Revolution.

During his first year in office Obama marked Nowruz with a then-unprecedented message offering Iran a "new beginning" of diplomatic engagement with the United States.

But Tehran rebuffed Obama's gesture and relations soured further when Iranian authorities cracked down on opposition protesters after a disputed election last June, drawing U.S. condemnation.

Iran's supreme leader, Ayatollah Ali Khamenei, has criticized Obama as merely a continuation of President George W. Bush's policies toward Israel. Khamenei has also called Israel a cancerous tumor that is on the verge of collapse and has called for its destruction.

Last year, Obama's message to the Iranians warned that better relations will not be advanced by threats. "We seek instead engagement that is honest and grounded in mutual respect."

Meanwhile, Russian Prime Minister Vladimir Putin told U.S. Secretary of State Hillary Clinton on Friday that Russia could back a sanctions resolution on Iran, Russian news agencies quoted a senior Putin aide as saying.

Putin's deputy chief of staff, Yuri Ushakov, was quoted as saying that Putin had affirmed that a sanctions resolution "was possible," Itar-Tass news agency reported.

"Vladimir Vladimirovich gave his appraisal of the situation in Iran and underlined that such a situation (involving Russian support of a sanctions resolution) was possible," RIA state news agency quoted Ushakov as saying.

But Putin also cautioned Clinton that sanctions "do not always help to resolve such an issue and that sometimes they can have a ounterproductive impact," Ushakov was quoted as saying by RIA.