(Reuters) - A federal judge said on Friday that Ohio's ban on recognizing the marriages of same-sex couples wed outside the state was unconstitutional and would be struck down later this month.

"I intend to issue a written decision and order by April 14 striking down as unconstitutional under all circumstances Ohio's bans on recognizing legal same-sex marriages from other states," U.S. District Judge Timothy Black said in a statement released by his chambers in Cincinnati.

Black issued the statement in a case involving four same-sex couples who were married legally in other states and are challenging Ohio's prohibition on recognition of both same-sex partners for births or adoptions.

The judge's statement, which did not address Ohio's ban on same-sex couples marrying within the state, came two weeks after another federal judge ruled neighboring Michigan's ban on gay marriage to be unconstitutional. The Michigan ruling has been appealed.

Seventeen states and the District of Columbia allow same-sex couples to marry. That number would increase substantially if a spate of federal court rulings striking down bans in several states are upheld on appeal.

The push to legalize same-sex marriage has gained momentum since a U.S. Supreme Court decision last year that ruled legally-wed gay couples are eligible for federal benefits.

(Reporting by David Bailey in Minneapolis; Editing by Cynthia Johnston and Paul Simao)

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