Talks between Russia and the United States were challenging but useful and the United Nations and other countries will be involved in additional discussions, a member of the Russian delegation told the TASS news agency.

"Everything was discussed - there was an intense, challenging dialogue, but it was very useful for us and for the Americans," Russian Senator Grigory Karasin was quoted as saying. "Many problems were discussed."

Karasin, a former diplomat, said that talks would continue and that the United Nations and other - unidentified countries - would be involved in them.

"We will continue to do this, involving the international community, first of all, the United Nations and individual countries," he said.

"In general, the impression was of a constructive dialogue, which is needed and necessary. The Americans are also interested in this," Karasin said.

A Russian source told Reuters that a draft joint statement had been sent to Moscow and Washington for approval, with the parties aiming to release it on Tuesday.