BRUSSELS, April 11 (Reuters) - Nippon Steel's ( NISTF )

$14.9 billion acquisition of U.S. Steel Corp will be

decided by European Union antitrust regulators by May 17, with

their approval a formality, a European Commission filing showed.

The Japanese steelmaker sought EU clearance on April 9, with

the EC reviewing the deal under a simplified procedure,

according to the filing.

Such a process is used for cases in which the EU competition

enforcer has no competition concerns, or the companies'

individual or combined market share is low.

Nippon Steel ( NISTF ), which clinched a deal to buy the 122-year-old

American steelmaker for a hefty premium in December, however,

faces headwinds with U.S. antitrust regulators.

Nippon Steel ( NISTF ) has manufacturing bases in Sweden, Finland and

Britain and an office in Germany while U.S. Steel has a

Slovakian subsidiary.