SINGAPORE (AP) — President Barack Obama said Sunday that "time is running out" for Iran to sign on to a deal to ship its enriched uranium out of the country for further processing, and Russian President Dmitry Medvedev said he still hopes to persuade Iran to send its enriched uranium to his country.

If that plan fails, however, Medvedev said other options remain on the table. While he did not cite those options, the Russian leader has said further sanctions against Iran were possible if it did not open its nuclear program to inspections to prove it was not trying to build a bomb.

Obama and Medvedev, meeting on the sidelines of the Asia-Pacific Cooperation Council, said Iran was one of the topics they discussed.

"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. "We are now running out of time with respect to that approach."

Russia and the U.S. are among six nations leading an effort to ensure Iran does not use what it maintains is a civilian nuclear program to develop an atomic bomb. But Moscow also has close ties with Iran and is helping build its first nuclear power plant, forcing Russia into a delicate balancing act.

Fears about the nature of Iran's nuclear program were heightened in September with the disclosure of a uranium enrichment facility near the holy city of Qom. U.N. inspectors visited the site last month, as the United States continued quiet preparations for the possibility of stiffening U.N. sanctions or those the United States has applied on its own.

Iran agreed to the inspections during a landmark meeting with the U.S. and other world powers at the beginning of October in Geneva, where the idea of Tehran shipping uranium to Russia for further enrichment was first raised.

Under the plan, Iran would send 2,420 pounds of low-enriched uranium to Russia in one batch by the end of the year in order to receive the nuclear fuel it needs for a research reactor that makes medical isotopes.

The United States supports such peaceful or beneficial uses of nuclear technology in Iran but has long suspected that part of the Iranian nuclear development program is aimed at covert production of a weapon.

The isotopes arrangement is a way to buy time and build confidence on both sides. By Western estimates, the plan would take put amounts of the low-enriched uranium Iran has stockpiled out of reach for conversion into the highly enriched fuel needed for nuclear weapons.