US President Barack Obama said Sunday he felt "reasonably good" about the chances of the Senate ratifying a major nuclear arms reduction pact with Russia this year.

The Obama administration has been locked in heated negotiations with Republican lawmakers over the Strategic Arms Reduction Treaty (START), which slashes US and Russian nuclear arsenals.

"My hope and expectation is that given this is a good treaty, given it has the support of previous Republican senior government officials, we should be able to get it done," Obama said aboard Air Force One as he flew home from a trip to Asia.

He noted Russia's cooperation with the United States on Iran sanctions and facilitating the transit of supplies into Afghanistan for US troops.

Obama earlier met his Russian counterpart Dmitry Medvedev on the sidelines of a Pacific Rim summit in Japan on the last day of his Asia visit.

The new US Congress takes office in January, with Republicans set to take control of the House of Representatives and to add members to the Senate after making huge gains in recent elections.

The next two months are therefore known as a "lame duck" session, potentially slowing progress on pushing the deal forward amid fears Republicans will stall to press for more concessions.

Obama said he felt "reasonably good about our prospects" for getting the treaty passed through lame duck session.

The START treaty, which was negotiated earlier this year to replace a similar treaty which expired at the end of December, faces stiff opposition in the United States amid fears it could hamper national missile defense plans.

The White House says ratifying the treaty is a vital national security priority, and failure to move on it would harm the "reset" in relations the Obama administration engineered between the two former Cold War foes.

Moscow said Friday it hoped the outcome of the US mid-term elections would not affect ties with Washington.

Under the US Constitution, treaties need the approval of two thirds of the Senate, meaning Obama's Democratic allies will need to pick up considerable Republican support.

The treaty -- signed by Medvedev and Obama at an elaborate ceremony in Prague in April -- restricts each nation to a maximum of 1,550 deployed warheads, a cut of about 30 percent from a limit set in 2002.

But a growing number of Republicans have voiced opposition, saying it would impede the US ability to set up missile defenses against future potential threats such as Iran.

During his talks with Medvedev, Obama assured the Russian president that passing the treaty this year was a "top priority."

Calling Russia an "excellent partner," he thanked Medvedev for his cooperation on Afghanistan and talked about a range of international issues including Sudan and the Middle East peace process.

The US president said he was "very pleased" with a "strong" Medvedev statement last week condemning a brutal attack on a leading reporter for the Kommersant newspaper.

Medvedev noted he had "seriously moved foreward" Russia's 17-year bid to join the World Trade Organization.

The country's accession process was held up by the United States in August 2008 after Russia's brief war with Georgia, but it was revived with the thaw in US-Russian relations under the Obama administration.