MOSCOW (Reuters) - Iran is ready for new talks with global powers on its nuclear program but the United States and others seeking to rein in its uranium enrichment activities need to be more constructive, Tehran's ambassador to Russia said on Monday.

Barack Obama's re-election has increased the chances of a revival of talks with Iran involving six world powers, but the envoy said the U.S. President should "change the conduct of the United States as regards Iran and choose a more logical approach."

Ambassador Reza Sajjadi said senior Iranian officials had conveyed Tehran's readiness for new negotiations to Russian Deputy Foreign Minister Sergei Ryabkov last week, but his remarks appeared to set a firm tone for any talks.

"We hope that in the next talks, the six nations - instead of (applying) a double standard, would approach these talks more constructively," Sajjadi told a news conference, speaking through an interpreter.

Three rounds of talks since April have failed to resolve the long dispute over Iran's nuclear program, which Western powers say is aimed at developing a nuclear weapons capability. Iran denies this, saying its program is entirely peaceful.

But neither side has been willing to abandon talks, in part because of concerns that Israeli could attack Iranian nuclear facilities, potentially igniting a new war in the Middle East.

The six nations leading diplomatic efforts with Iran - permanent U.N. Security Council members the United States, Britain, France, Russia and China, as well as Germany - meet on Wednesday to discuss negotiating strategy.

(Writing by Steve Gutterman)