WASHINGTON — Legislation to avert a Jan. 1 increase in income tax rates has gained 60 votes in the Senate, the level needed to advance toward a final vote.

The roll call is continuing, and the test vote is not final. But the bipartisan show of support is a strong indication the measure will be passed and sent to the House, possibly as early as Tuesday.

The bill provides a two-year reprieve in the tax increases that are scheduled to take effect on Jan. 1 at all income levels. It also reduces Social Security taxes for every wage earner in 2011 and extends an expiring program of jobless benefits for the long-term unemployed.