DETROIT — A healthier economy and more model introductions should push U.S. auto sales above the 15 million mark this year, an industry research firm predicts.

The Polk firm said auto sales should continue to lead the country’s economic recovery, rising nearly 7 percent over 2012 to 15.3 million new vehicle registrations.

Automakers release December and full-year sales for 2012 on Thursday. Analysts said sales reached 14.5 million last year, the strongest performance since 2007 – just before Americans felt the impact of the recession. Sales of more than 15 million are considered a sign of health for the auto industry and the economy, many analysts say.

Polk does not expect pre-recession sales levels of 17 million for several more years, Anthony Pratt, Polk’s forecasting director for the Americas, said Wednesday.

Polk expects 43 new models to be introduced this year, up 50 percent from last year. New models usually boost sales. The company also predicts a rebound in sales of large pickups and midsize cars.

But Polk’s optimistic forecast hinges on Washington reaching an agreement on spending cuts, which could happen later in the year. On New Year’s Day, Congress approved a compromise to avoid the fiscal cliff. The deal raises taxes for incomes exceeding $400,000 for individuals and $450,000 for couples. But it delayed action on dramatic federal spending cuts and debt, setting up another showdown in a divided Congress.

Those first showdowns will come over the next three months, when the government’s legal ability to borrow money will expire and temporary financing for federal agency budgets will expire.