MILWAUKEE (AP) -

Four Wisconsin paper mills are expected to merge under new ownership into the state's biggest papermaking company by employment.

The Milwaukee Journal Sentinel reports the New York private equity firm, KPS Capital Partners LP, has agreed to acquire Rhinelander and Mosinee paper mills from Wausau Paper Corp. and the Kaukauna and De Pere mills from Thilmany Papers.

KPS previously has said it cannot finalize its acquisitions until a new union contract is approved.

But the United Steelworkers has ratified a four-year collective bargaining agreement for three of the mills, which is expected to clear the way for the merger. The De Pere is a nonunion mill.

The new paper company will employ 1,800 in the state. It doesn't yet have a formal name.