By Thomas Ferraro

WASHINGTON (Reuters) - A long-delayed vote to appoint the United States' top financial diplomat came a step closer on Monday as the Senate ruled to end debate on the issue.

Lael Brainard's nomination to become under secretary for international affairs at the U.S. Treasury has been stalled for more than a year because of objections by some Republicans.

The 84-10 Senate vote on Monday topped the 60 needed to break that deadlock. A final vote, which is expected to be for Brainard's confirmation, could come as early as Tuesday.

The timing of the vote to end debate, and the expected confirmation vote, is significant as it occurred just before meetings this week of the Group of 20, the smaller Group of Seven and the International Monetary Fund and World Bank.

If confirmed, Brainard would hold a key position at Treasury in efforts to persuade China to adopt a more flexible currency

Brainard's nomination was slowed initially by a probe into her taxes. She faced scrutiny over deductions made for a home office, late payments of some property taxes and verification of legal status for household employees.

During debate leading up to Monday's ruling, Democratic Sen. Max Baucus of Montana, said Brainard had the qualities needed to help plot a stronger course for the United States and global economy.

"She will work with key trading partners such as China and the European Union," said Baucus, chairman of the Senate Finance Committee. "And she must help to guide our country from an economic recovery to economic growth."

As well as holding a key position in talks with China, Brainard would help shepherd U.S. official positions through the global lending agencies that are being urged to take on a stronger role in monitoring global currency policies.

The Senate Finance Committee approved Brainard in December, 15-8. But at least one Republican managed to delay consideration by the full chamber, a Republican aide said.

The ranking Republican on the Senate Finance Committee, Sen. Charles Grassley of Iowa, said the delay in Brainard's nomination had nothing to do with partisan politics.

"The only basic issue should be that everyone needs to pay their taxes as required by law and the nominee should be fully responsive to the Congress," Grassley said, adding: "In looking at the first of these issues, the nominee showed that she was deficient in the second."

Brainard worked at the White House for former President Bill Clinton and was later a senior fellow at the Brookings Institution in Washington.

During the past year she has maintained a low profile, advising at Treasury but avoiding any contact with reporters during the administration's efforts behind the scenes to move her nomination forward.

Treasury is also preparing for the annual meeting in Beijing of the Strategic and Economic Dialogue, which occurs at a sensitive time as the Obama administration tries to keep momentum going for China to let its currency, the yuan, appreciate.

Geithner recently paid a surprise visit to Beijing and has been vocal in saying he wants China to adopt a more flexible currency, which he says would be in its own interest. Brainard would take over part of that role as the department's point person on key international issues.

(additional reporting by Glenn Somerville)

(Reporting by Thomas Ferraro; Editing by Andrew Hay)