(Changes attribution, adds details)
TOKYO, April 18 (Reuters) - Japanese Prime Minister Shinzo Abe spoke by telephone to U.S. Vice President Joe Biden on topics including the situation in Ukraine and trade negotiations, an Obama administration official said.
U.S. President Barack Obama said on Thursday talks between Russia and Western powers aimed at ending tensions in Ukraine have potential but that Washington and its allies are prepared to impose more sanctions on Moscow if the situation fails to improve.
The U.S. official said the phone conversation touched on Obama's April 23-25 visit to Japan, talks on the U.S.-led Trans-Pacific Partnership (TPP) multilateral trade deal, and Ukraine.
Tokyo and Washington are trying to narrow gaps hampering a bilateral trade deal seen as vital to the broader regional TPP ahead of Obama's summit with Abe.
(Reporting by Kaori Kaneko; Additional reporting by Steve Holland in Washington; Editing by Dominic Lau and Paul Tait)