A nuclear deal with Iran would be a diplomatic victory for Barack Obama, but its historic worth and impact on the U.S. president's legacy may not be known for a decade or more.

In July 2007, a dark-haired, fresh-faced U.S. Senator was asked if he would meet the leaders of Iran, Syria, Venezuela, Cuba and North Korea without precondition in the first year of his presidency.

The U.S. hunkered down Tuesday with Iran for crunch talks while warning that key disagreements remain ahead of a March 31 deadline to agree the outlines of a major nuclear deal.

"There is no way around it, we still have a ways to go," a senior U.S. official involved in the talks in the Swiss lakeside city of Lausanne said Tuesday.

Iran nuclear talks entered a critical week Monday with U.S. Secretary of State John Kerry and his Iranian counterpart racing to find an elusive breakthrough after a negotiating marathon that began in 2013.

Time is running out, with Kerry and Mohammad Javad Zarif aiming to agree the outlines of a potentially historic agreement by the end of the month. A full accord is then due by July 1.

An Iranian general who has been a key adviser in Iraq's fightback against the Islamic State group was voted Iran's person of the year in an annual poll released Sunday.

General Qassem Suleimani, commander of the Quds Force, the foreign operations arm of Iran's Revolutionary Guards, won 37 percent of the votes cast in the survey to mark the Persian New Year, Nowruz.

As the drive to reach an accord with Iran on its nuclear program heads towards a March 31 deadline, France is digging into its role as chief hawk -- a position inclined to annoy U.S. allies, but not likely to scuttle an eventual accord, diplomats say.

The French hard-line among its U.S., British, Chinese, Russian and German partners to hammer out a nuclear agreement with Tehran is rooted in ideological, historical, and even personal concerns that tend to stiffen as Paris recognizes Washington's increasing pragmatism in seeking to conclude a deal swiftly.

Iran and the U.S. were racing against the clock Sunday to close in on a nuclear deal with US Secretary of State John Kerry saying it was "time to get it done" after 18 months of intense negotiations.

U.S. Secretary of State John Kerry said on Saturday that talks on Iran's disputed nuclear program have made progress, but there were still "important gaps" to overcome.

Kerry, who is attending a three-day international investor conference in Egyptian resort town of Sharm el-Sheikh, said the purpose of these talks was "not just to get any deal, it is to get the right deal".

The U.S. has failed to live up to its promises to help Iraq fight Islamic State extremists, unlike the "unconditional" assistance being given by Iran, the commander of Iraq's powerful Shiite militias alleged Friday.

In a battlefield interview near Tikrit, where Iraqi forces are fighting to retake Saddam Hussein's hometown from the militants of the so-called Islamic State, commander Hadi al-Amiri criticized those who "kiss the hands of the Americans and get nothing in return."

Republicans hammering the Obama administration about nuclear talks with Iran have stepped up their criticism on a second front: accusing President Barack Obama of being so keen to strike a deal that he's ignored Iranian moves to expand its influence across the Middle East.

Republican Party hawks maintain that Obama wants so much to burnish his legacy with an agreement to restrain Iran from becoming a nuclear-armed state that he is not pushing back against Iranian activities in Iraq, Yemen, Syria, Lebanon and Bahrain. Secretary of State John Kerry has defended the administration repeatedly against a barrage of questions from lawmakers, including some who insist that the nuclear negotiations have hamstrung U.S. policy decisions in the region.

Iran nuclear talks enter their critical end-game Sunday with U.S. Secretary of State John Kerry due to meet his Iranian counterpart in Switzerland as a March 31 deadline looms and a political storm rages in Washington.

After a decade of crisis, 18 months of talks and two missed deadlines, six world powers aim by the end of this month to nail down the outline of a deal with Iran that would put making a nuclear bomb out of Tehran's reach.