Seventy-six US senators have urged President Barack Obama to impose tougher sanctions on Iran, saying Washington must stress its military option even as new President Hassan Rowhani urges dialogue.

"Mr. President, we urge you to bring a renewed sense of urgency to the process," said the letter, publicized Monday by authors Robert Menendez, the Democratic chairman of the Senate Foreign Relations Committee, and Republican Senator Lindsey Graham.

"We need to understand quickly whether Tehran is at last ready to negotiate seriously" on its nuclear program, it said.

Another 74 senators signed the letter, which was sent to the White House on Friday, two days before Rowhani was sworn in in Tehran.

The reputed moderate once served as Iran's nuclear negotiator, and the West is hoping that he will take a more constructive approach in long-running talks on Tehran's controversial nuclear drive.

Despite Iranian denials, the West is convinced Tehran is pursuing a nuclear bomb.

"Iran has used negotiations in the past to stall for time, and in any event, (supreme leader Ayatollah Ali) Khamenei is the ultimate decision-maker for Iran's nuclear program," the senators wrote to Obama.

"Iran needs to understand that the time for diplomacy is nearing its end. We implore you to demand immediate serious moves on Iran's part."

The White House said Sunday that Iran will find the United States a "willing partner" if Rowhani is prepared for serious nuclear talks.

Last week shortly before Congress went on summer break, the House of Representatives overwhelmingly approved harsh new sanctions aimed at drastically reducing Iran's oil exports by ending purchasing exemptions to countries like China and Japan.

The recess window is being seen as a pivotal period for both the White House and Iran.

A Senate official told AFP that after the August recess the Senate Banking Committee aims to introduce legislation on further sanctions against the Islamic republic.

"Our nation must toughen sanctions and reinforce the credibility of our option to use military force," the senators wrote.

"We must be prepared to act, and Iran must see that we are prepared."

Rowhani inherits a turbulent nation that is struggling economically, largely due to crippling sanctions already on the books.

But he insisted Sunday that "if you want a proper answer, do not speak with Iran with the language of sanctions but with the language of respect."

EU calls for 'rapid progress' on Iran nuclear issue
Brussels (AFP) Aug 05, 2013 - The European Union urged Iran's new president Monday to make "rapid progress" towards resolving concerns over the country's disputed nuclear programme after he struck an apparently more conciliatory stance.

The West is hoping that President Hassan Rowhani will take a more constructive approach in the long-running talks on Tehran's nuclear drive, which despite Iranian denials is suspected by world powers of having military objectives.

On Sunday, he repeated his campaign promise to help Iranians who are struggling under the weight of US and EU economic sanctions and called for "mutual respect" with the West, striking a sharply different tone from his predecessor.

"We take note of the new President's words," said Michael Mann, spokesman for EU foreign affairs head Catherine Ashton, who has led talks with Tehran on the nuclear dispute.

"We hope that the new Iranian government will be prepared to make rapid progress towards addressing international concerns about its nuclear programme and engage constructively on the (P5+1) proposal for confidence-building," Mann said.

Western powers believe the Iranian nuclear programme is being used to develop an atomic bomb, but Tehran insists it is for peaceful purposes.

In his inaugural speech Sunday, the new president said Iranians were under "a lot of economic pressure" because of tough US and EU sanctions over Iran's refusal to stop uranium enrichment.

"The only path to interact with Iran is through negotiations on equal grounds, reciprocal trust-building, mutual respect and reducing hostilities," he said.

"If you want a proper answer, do not speak with Iran with the language of sanctions but with the language of respect," Rowhani added.

The White House said Iran would find the United States a "willing partner" if Rowhani was serious.

Ashton is lead negotiator with Iran for the P5+1 group, which is made up of the five permanent UN Security Council members, Britain, China, France, Russia and the United States plus Germany.

She met Iran's top nuclear negotiator Saeed Jalili in Istanbul in May for talks he described as "long and useful" after fruitless discussions the previous month in Almaty, Kazakhstan.

US and EU sanctions have crippled Iran's once lucrative oil sector, cut its access to global banking and contributed to soaring inflation and a shrinking economy.