SINGAPORE (Reuters) - U.S. President Barack Obama said Sunday time was running out for diplomacy to resolve a crisis over Iran’s nuclear program, but Russian President Dmitry Medvedev offered softer criticism of Tehran.

Slideshow ( 2 images )

The United States had been willing to give Iran time to decide whether to accept a U.N.-brokered deal meant to allay suspicions it is after atomic bombs but which has drawn Iranian objections, a U.S. diplomat said a week ago.

Sunday Obama, speaking after talks with Medvedev on the sidelines of an Asia-Pacific meeting in Singapore, suggested patience was running low.

“Unfortunately, so far at least, Iran appears to have been unable to say yes to what everyone acknowledges is a creative and constructive approach,” Obama said while seated next to Medvedev.

“We are running out of time with respect to that approach.”

Repeating previous Russian language, Medvedev said “other means” could be used if discussions did not yield results, but did not specify what they might be.

“Thanks to joint efforts the process of (the Iran talks) has not stopped but we are not completely happy about its pace. If something does not work there are other means to move the process further,” he said.

“Our aim is clear -- a transparent nuclear program rather than a program which causes others’ concern.”

In talks with six powers in Geneva on October 1, Iran had agreed in principle to send the bulk of its low-enriched uranium to Russia and France for further processing and conversion into fuel plates for the Tehran reactor, Western officials said.

The plan for Iran to part with stocks of potential nuclear explosive material in exchange for fuel to keep a nuclear medicine facility running has subsequently stumbled on Iranian calls for amendments and more talks, which Washington has rejected.

Iran’s pledges in Geneva won itself a reprieve from sanctions targeting its oil sector but Western powers stressed they would not wait indefinitely for Tehran to follow through.

Russian officials such as foreign minister Sergey Lavrov have said Washington was trying to push Moscow into a position of publicly threatening imposition of sanctions soon if Iran did not play ball.

Iran says it is enriching uranium only for power plant fuel, not for nuclear warheads. But its history of nuclear secrecy and continued restrictions on U.N. inspections have raised Western suspicions Iran is latently pursuing nuclear weapons capability.