The U.S. Senate decided on Tuesday to bring full vote on a nuclear arms treaty with Russia, long sought by President Barack Obama and the Democrats.

The Senate voted by 67-28 to end debate on the new Strategic Arms Reduction Treaty (START) and move on to vote on it. As at least 10 Republican senators have publicly pledged to back the pact, its passage seems to be a sure thing.

Obama sees the pact's passage this year as his last priority for the current Congress session which is in its waning days. For the past days, he joined Vice President Joe Biden and Secretary of State Hillary Rodham Clinton in calling wavering Republican senators to line up their support for it.

Obama wrote on Saturday to Senate Republican leaders to try to assuage some Republicans' concern about the pact's possible limit on U.S. missile defense system, assuring them that "as long as I am president, and as long as the Congress provides the necessary funding, the United States will continue to develop and deploy effective missile defenses to protect the United States, our deployed forces and our allies and partners."

He also wrote to some senators to assure them about his commitment to modernizing U.S. nuclear arsenal with a spending of some 85 billion dollars over 10 years.

Following demand on Monday for the Senate to act quickly by Mike Mullen, chairman of the U.S. Joint Chiefs of Staff, Defense Secretary Robert Gates issued a statement on Tuesday, urging the Senate to ratify the pact this week.

At least 10 Republican senators said early Tuesday that they would back the treaty. A final vote is expected on Wednesday.

For the treaty to pass the 100-member Senate, a two-thirds majority of those voting is needed. The Democrats have 58 votes in their caucus with one expected absent due to a prostate cancer surgery.

"I think it's going to pass and more than just pass," said Republican Senator Bob Corker, who has agreed to throw his weight behind the accord.