Moscow, May 28 (IANS/RIA Novosti) Russia and the US are unlikely to agree on the missile defence issue by the end of US President Barack Obama's term, said US Ambassador to Russia, John Beyrle Friday.

"I think Russia and the United States will not manage to reach a consensus on this issue by the end of Obama's presidential term," Beyrle said in Russian during an interview with Ekho Moskvy radio station.

Earlier Friday at the G8 summit in Deauville, Russian President Dmitry Medvedev expressed his dissatisfaction with how the negotiations with the US on the missile defence shield are continuing, saying the sides are wasting time.

Moscow has been concerned by US reluctance to provide legally binding guarantees that its European missile defence system will not be directed against Russia.

"We must receive guarantees that it is not directed at us. So far, no such guarantees have been given," Medvedev said.

Medvedev warned last Wednesday that Russia would have to build up its nuclear capability if NATO and the US failed to reach an agreement with Moscow on European missile defence cooperation.

Moscow has warned it might pull out of the new START Treaty.