SINGAPORE — A major pact within tantalizing reach, President Barack Obama aims to nudge forward an arms-control deal in talks with Russian President Dmitry Medvedev.

The 21-nation Asia-Pacific Economic Cooperation forum brought Obama to Singapore, but he is focusing on individual meetings Sunday with Medvedev and with Indonesia's Susilo Bambang Yudhoyono, president of the world's largest Muslim nation and Obama's home as a boy. The U.S.-Russia meeting takes place as the nations seek a successor to a Cold War-era agreement.

Obama planned another milestone: joining a larger meeting that includes the leader of military-ruled Myanmar. Obama is sure to face criticism at home, particularly from conservatives, for doing so — a significant step up in his administration's new policy of "pragmatic engagement" that is a shift from years of U.S. isolation and sanctions.

The leaders at the APEC forum also planned an informal breakfast meeting, organized by Australian Prime Minister Kevin Rudd and Mexican President Felipe Calderon, to discuss the progress of negotiations on a climate change agreement. The prime minister of Denmark, Lars Loekke Rasmussen, the chairman of next month's U.N. climate conference in Copenhagen, was expected to attend.

Obama and Medvedev agreed in April to reach a new nuclear arms reduction treaty to replace Strategic Arms Reduction Treaty 1 before it expires on Dec. 5. Later, in Moscow in July, they agreed further to cut the number of nuclear warheads each nation possesses to between 1,500 and 1,675 within seven years.

U.S. officials say that the two nations now have agreed on the broad outlines of a new treaty, with the expectation that the leaders will sign one during Obama's travels to Europe in early December to accept the Nobel Peace Prize.

Such an agreement would be a big feather in Obama's cap and bragging rights toward his promise to work toward a nuclear-free world, offering momentum for other arms-control and nonproliferation efforts. The president has been hinting at his optimism on the issue leading up to and during his Asia trip.

"We are already taking steps to bring down our nuclear stockpiles in cooperation with the Russian government," he said during a news conference in Japan with Prime Minister Yukio Hatoyama.

A new treaty also could boost relations with Russia at a time that Washington is looking for its cooperation on issues including reining in Iran's nuclear ambitions.

Negotiators already have worked through a number of contentious issues and agreed on the number of warheads, the number of delivery systems and what will count as a delivery system, officials said.