UPDATE 1-Trump, Erdogan agree to meet at G-20 in June -Turkish official

Turkish President Tayyip Erdogan and U.S. President Donald Trump agreed in a phone call on Wednesday to meet on the sidelines of a G-20 meeting set for June 28-29 in Japan, the Turkish Presidency's communications director said.

Ties between the NATO allies have recently been shaky over Ankara's decision to purchase the Russian S-400 missile system, which Washington says could compromise its F-35 fighter jets. Turkey has offered that the two countries form a working group that would asses the potential impact of the S-400s on the aircraft but has yet to hear back from the United States.

Fahrettin Altun, the communications director, said on Twitter that Erdogan reiterated to Trump during Wednesday's call Turkey's offer to form the working group. Washington has threatened to impose sanctions on Turkey if it goes through with the purchase, a move that would likely damage Turkey's economy. The lira has already declined about 14% this year in part on concerns over the potential sanctions.

Altun said that the call involved discussions over a range of bilateral and regional issues, but he did not specify. The allies are also at odds over various other issues, including policy differences in Syria and U.S. sanctions on Iran. (Reporting by Can Sezer and Ece Toksabay Writing by Ezgi Erkoyun; Editing by Jonathan Spicer)