TEHRAN  - Iran is committed to securing a nuclear agreement with world powers but will not sign one "at any price", its negotiators said Monday, as a key deadline for Tehran nears. Iran and the five permanent members of the UN Security Council plus Germany - known as P5+1 - signed an interim deal last November and are in discussions to secure a more permanent accord.

The target date for a final deal has been put back to November 24.

"We are entering with goodwill into further negotiations with the P5+1 group and we want to reach an agreement... but we are not willing to pay any price," ISNA news agency quoted Majid Takht-Ravanchi, one of Iran's main negotiators, as saying. "If the other side also show goodwill we can reach an agreement by November 24," he added.

By August 25 Tehran must also respond to the International Atomic Energy Agency (IAEA) on decade-old allegations of past nuclear weapons research.

Tehran denies it wants nuclear weapons, insisting it is pursuing atomic energy purely for peaceful purposes.

Meanwhile, the UN atomic watchdog's chief said Monday that Iran had begun to answer long-held allegations of efforts to develop nuclear weapons ahead of an August 25 deadline. Returning from Tehran where he met with President Hassan Rouhani and top Iranian nuclear officials, IAEA chief Yukiya Amano said that Iran had started carrying out crucial measures agreed in May to clear up claims it has done research into nuclear weapons.

This included two measures related to the so-called "possible military dimensions" (PMD) of Iran's nuclear programme, which Tehran insists is entirely peaceful.

"We have started the implementation of the five measures including PMD," Amano told journalists on arrival at Vienna airport.  He did not give any details about the process however and refused to say if Iran would be able to complete it by the deadline next Monday.

"We have started and that is important and I expect that progress will be made over the next week," Amano said, adding that some of his team had stayed behind to continue inspections of Iranian nuclear facilities.  Answering the PMD allegations is an important part of a comprehensive agreement that world powers and Iran are trying to nail down by November 24.

In May, the International Atomic Energy Agency announced Tehran had for the first time in six years shared information regarding this issue with the nuclear watchdog.

Iran insists its nuclear drive - which has been expanding steadily for the past decade - is solely for civilian purposes but the West has long believed it is seeking an atomic bomb.

On Monday, Amano noted that the IAEA had "received additional clarification" from Iran regarding sophisticated explosive detonators that can be used in a nuclear bomb but also have other applications.

He added that new measures - a fourth series to follow the ones from May - were also in the works.  "We have started the discussion on the new practical measures to be taken up as a new step," Amano said. "I hope and I expect that we can reach agreement soon," he added.