US Vice President Joe Biden on Friday warned Iran that opportunities for diplomacy over its disputed nuclear programme were not unlimited but offered direct talks between Washington and Tehran.
In an interview with the German Sueddeutsche Zeitung daily, Biden said the "burden of proof" that Iran was not seeking a nuclear weapon lay with the authorities in Tehran.
"President (Barack) Obama has made clear that containment is not an option. We will prevent Iran from getting a nuclear weapon," Biden was quoted as saying in remarks published in German.
"We think there is time and space for diplomacy -- accompanied with economic pressure. But this window will not be open for an unlimited time," he added.
He said Tehran could expect continued sanctions and increasing international pressure over its disputed nuclear drive, which Iran insists is entirely peaceful.
Iran and six world powers -- the US, China, Russia, Britain, France and Germany -- held three rounds of talks last year aimed at easing the standoff over Iran's nuclear activities.
The six, known as the P5+1, called on Iran to scale back its programme but stopped short of meeting Tehran's demands to scale back sanctions. The last round ended in stalemate in June in Moscow.
Biden said: "We are continuing with the P5+1 group to work for a diplomatic solution and we have said from the beginning that we are prepared to hold a bilateral meeting."
"The goal of the sanctions is not punishment. Iran must be persuaded that it has to live up to its international commitments," added Biden.
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Another round of talks was initially expected to be held in December or January but a date and a location have still not been set, amid indications that neither side is prepared to change substantially its position.
Parallel talks between Iran and the International Atomic Energy Agency are set to resume on February 13 in Tehran.
Speaking to reporters later, German Foreign Minister Guido Westerwelle said he planned to meet his Iranian counterpart Ali Akbar Salehi over the weekend and urged Tehran to consider Biden's offer of bilateral talks.
"This is a hand that he is extending to the Iranian government and we will urge the Iranian government to take them up on this offer," Westerwelle said after meeting EU's foreign policy chief Catherine Ashton.
"Direct talks between Washington and Tehran are in the interest of all of our security, also in our interests as Europeans so we will make our contribution to creating the necessary atmosphere," added the minister.
For her part, Ashton said she hoped talks would resume "very shortly."
Biden is in Germany for a European trip that will also take in France and Britain.
He will meet Chancellor Angela Merkel later Friday before travelling to the southern city of Munich for the 49th edition of the Munich Security Conference, an annual gathering of defence officials and top brass.
He will deliver a speech on foreign policy there on Saturday and hold talks with Russian Foreign Minister Sergei Lavrov, UN-Arab League peace envoy Lakhdar Brahimi and Syrian opposition chief Moaz al-Khatib.
Westerwelle played down the likelihood of direct US-Iran talks in Munich saying it was "not the right venue for this kind of thing."
Biden will visit US troops in Germany on Sunday before heading to Paris on Monday for talks with French President Francois Hollande. The following day, he travels to London to meet Prime Minister David Cameron.