While Tehran and the UN atomic watchdog agreed on January 13 to answer all the questions within four weeks, Bulgarian Foreign Minister Ivaylo Kalfin said Iran was now aiming for an accord by "the end of February or the beginning of March."

Kalfin said his Iranian counterpart Manouchehr Mottaki assured him in talks in Sofia on Tuesday that Iran was working "very actively" with the International Atomic Energy Agency.

Tehran had already answered "70 percent of a detailed questionnaire" about its disputed atomic drive and would respond "completely and clearly by end-February or the beginning of March," Kalfin said.

Under a so-called "work plan" agreed between the IAEA and Tehran in August, Iran originally had until the end of the year to clear up all outstanding issues related to its past and present nuclear activities.

But following a meeting between IAEA chief Mohammed ElBaradei and Iran's leaders earlier this month, Tehran agreed to complete the work plan "within four weeks", ie. mid-February.

The latest comments suggest the deadline is slipping once again as Iran appears to be stalling for yet more time.

"In his (Motakki's) views, until this process has been completed within the next month or month-and-a-half, there should be no other sanctions, including ones by the (UN) Security Council," Kalfin said.

In Berlin on Tuesday, the so-called P5+1 states -- Britain, China, France, Russia and the United States plus Germany -- were meeting to discuss a possible third round of sanctions against the Islamic republic in efforts to force it to back down in the long-running nuclear standoff.

Western countries, and the United States in particular, accuse Iran of seeking to develop an atomic bomb, a charge Tehran vehemently denies.

The West insists Iran suspend its sensitive uranium enrichment activities to prove its aims are entirely peaceful, as it claims.

But Tehran refuses outright, insisting it has a right to develop nuclear technology to provide energy for its growing population.

It has so far defied two rounds of UN sanctions and the P5+1 states were meeting in Berlin on Tuesday to discuss a possible third round.

China and Russia, which have lucrative trade ties with the Islamic republic, have been reluctant to back any more punitive measures.

Motakki insisted in Sofia that Iran was "cooperating with the IAEA" with a view to clearing up the outstanding questions.

"Our two countries believe that the nuclear programme can have no other purposes than peaceful ones. We are against the proliferation of weapons of mass destruction," Motakki said.

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