But only if the Mullahs are “serious” or something.

MUNICH — The United States is prepared to engage in direct talks with Iran over its contentious nuclear program, Vice President Biden said Saturday, although he added that the administration would negotiate only if Iranians were “serious.”

Talks have been offered in the past, but they have never materialized, and last month Iran defiantly said it planned to accelerate its enrichment of uranium. Biden said that it was not too late to reach an agreement on Tehran’s nuclear ambitions.

“Our policy is not containment,” the vice president told an annual gathering of security officials and world leaders in Munich. “It is to prevent Iran from acquiring a nuclear weapon.”

During a weekend of frenzied diplomacy in this elegant German city, Biden and Iranian Foreign Minister Ali Akbar Salehi were in the same building at the same time, but they did not meet. One-on-one contact, Biden said, could take place only after American officials are convinced that negotiations would be fruitful.