May 30 (Reuters) - U.S. Steel Corp (X.N), opens new tab and Japan's Nippon Steel (5401.T), opens new tab have received all regulatory approvals outside of the United States for their proposed $14.9 billion merger, the companies said on Thursday.

Nippon had clinched the deal to buy U.S. Steel last December, after edging out rivals including Cleveland-Cliffs (CLF.N), opens new tab, ArcelorMittal (MT.LU), opens new tab and Nucor (NUE.N), opens new tab.

The steelmakers now need to secure an approval in the U.S., where the deal is facing regulatory scrutiny and increasing political opposition including from President Joe Biden, who wants U.S. Steel to remain domestically owned.

The proposed transaction is also facing opposition from the powerful United Steelworkers union over fears of job losses, and is being scrutinized by the U.S. Department of Justice. Nippon had sought to address the concerns by pledging to honor all agreements in place between U.S. Steel and the union.

It had also said it would move its own U.S. headquarters to Pittsburgh where U.S. Steel is based. The companies reiterated on Thursday that they expect the deal to be completed in the second half of this year.

"U.S. Steel and Nippon Steel are committed to, as in the months past, continuing to fully cooperate with the examination of the relevant authorities and are determined to complete the transaction," they said.

The proposed transaction has now received approvals from the European Commission and the regulatory authorities of Mexico, Serbia, Slovakia, Turkey and the United Kingdom. Shares of U.S. Steel were up 1.7% at $37.77 in early trading.

U.S. Steel shareholders had in April voted in favor of the deal, which would help Nippon — the world's fourth-largest steelmaker — move towards its goal of having 100 million metric tons of global crude steel capacity.