Iran's nuclear program will top the agenda at talks to be held next week between German ChancellorAngela Merkel and Russian President Vladimir Putin, a German government spokesman said on Wednesday.

The meeting will take place in the Russian city of Tomsk on April 26-27.

Iran's uranium enrichment activities are "steps in the wrong direction" and will lead to Tehran's self-isolation, deputy government spokesman Thomas Steg said, adding "What Tehran is doing will not be tolerated by the international community."

"The German government's view that a diplomatic solution is needed remains unchanged."

Deputy foreign ministers of the five permanent members of the UN Security Council -- the United States, Russia, China, France and Britain -- and Germany met in Moscow on the Iranian nuclear issue, but ended on Tuesday night without any decisions being made.

German foreign ministry spokesman Jens Ploetner downplayed reports that talks in Moscow failed to bridge differences over possible sanctions, saying "no concrete results were expected".

This was just a half-way point in a 30-day deadline set by the UN Security Council for Iran to give up its uranium enrichment program.

The deadline will expire on April 28, one day after the Merkel-Putin talks.