Experts from the UN nuclear watchdog held talks in Tehran Monday in their investigation into decade-old allegations of possible military dimensions to Iran's nuclear programme, the ISNA news agency reported.

"Additional information was exchanged. We have decided to carry on with our cooperation," said Iran's ambassador to the International Atomic Energy, Reza Najafi, as state television announced the end of the talks.

"The meeting was very serious and the discussions technical. The exchanges of questions and answers show that the two parties are serious," he said, adding that another meeting would take place in the second half of April.

The IAEA delegation's visit came as the United States and other major world powers seek to conclude a comprehensive agreement on Iran's controversial nuclear activities.

While Iran is negotiating limits on its programme with world powers, the IAEA has been pressing leaders in Tehran for years to address allegations that prior to 2003, and possibly since, they conducted research into the technology required to build a nuclear weapon.

In 2011, the IAEA expressed concern about Iran's development of "exploding bridge wire detonators" because of their "possible application in a nuclear explosive device".

It is one of a number of allegations of past weapons research which Tehran denies but which the watchdog says it has yet to satisfactorily answer.

Another technical issue to be discussed during the visit concerns "modelling and calculations" on neutrons, the sub-atomic particles which trigger the fission of uranium, ISNA reported.

After some progress last year, the IAEA investigation stalled.

In its latest report on February 19, the IAEA said Iran had not provided "any explanation regarding the two outstanding practical issues".

But a spokesman for Iran's Atomic Energy Agency told state television on Sunday that "these two issues can be finalised during the visit of the IAEA delegation".

IAEA chief Yukiya Amano has urged Iran to provide answers quickly.

White House decries Republican effort to derail Iran talks
Washington (AFP) March 9, 2015 - The White House on Monday denounced efforts by Republican lawmakers to "throw sand in the gears" of sensitive talks over Iran's nuclear program as "partisan."

Forty-seven Republicans, including Senate leaders and several potential 2016 presidential candidates, wrote an open letter to Iran's leader, warning any deal with President Barack Obama might not be honored in future.

The White House responded angrily, accusing the Senators of interference and continuing a "partisan strategy to undermine the president's ability to conduct foreign policy and advance our national security."

"It raises significant questions about the intent or the aims of the authors," said spokesman Josh Earnest, who accused the senators of establishing a "back channel" with hardliners in Tehran.

With a March deadline looming, negotiators are furiously working to agree a deal that would curb Iran's nuclear program in return for reducing Western sanctions.

The deal is seen as a key foreign policy goal of the Obama administration.

Earnest also accused Republicans of supporting airstrikes against Iran's facilities that the White House says would only temporarily set Iran's program back.

"The rush to war, or at least the rush to the military option that many Republicans are advocating, is not at all in the best interests of the United States," said Earnest.

He said the senators' actions were not in keeping with the role that America's founding fathers envisioned for the legislative branch.