In its annual report on global threats, Austria's domestic intelligence service (DSN) said Monday that Iran's "nuclear weapons development programme is well advanced".

The United States, Israel and other Western countries have repeatedly accused Iran of seeking to acquire a nuclear weapon.

Iran has categorically denied the claims, instead arguing that it is pursuing a nuclear programme for civilian purposes alone.

According to the International Atomic Energy Agency (IAEA), however, Iran is the only country in the world that enriches uranium up to 60 percent.

That rate is still below the 90 percent threshold required for a nuclear weapon, but far above the 3.67 percent limit set under a 2015 agreement with world powers.

"All efforts to prevent Iran's armament through sanctions and agreements have so far proved ineffective," the Austrian report said.

On Friday, Iran's foreign ministry condemned "the fake information" disseminated in the report and demanded an explanation from the Austrian government.

The IAEA, whose headquarters is in the Austrian capital, will in coming days publish its own review of Iran's nuclear activities.

Iran and the United States are engaged in an Omani-mediated effort to reach a deal on Tehran's nuclear programme, after Donald Trump during his first presidency pulled out of the 2015 agreement.

No date has yet been set for the next Iran-US meeting since last week's discussions in Rome.

On Thursday, Foreign Minister Abbas Araghchi said he was "not sure" that a deal with the United States was imminent.

His statement came after Trump said on Wednesday that the two sides were "very close to a solution".