FILE PHOTO: U.S. President Donald Trump speaks at the National Association of Realtors' Legislative Meetings & Trade Expo in Washington, U.S., May 17, 2019. REUTERS/Carlos Barria

WASHINGTON (Reuters) - U.S. President Donald Trump threatened Iran in a tweet on Sunday, raising concerns about a potential U.S.-Iran conflict at a time when tensions between Washington and Tehran have risen.

“If Iran wants to fight, that will be the official end of Iran. Never threaten the United States again,” Trump said in a tweet.

Trump has tightened economic sanctions against Iran, and his administration says it has built up the U.S. military presence in the region. It accuses Iran of threats to U.S. troops and interests.

Tehran has described U.S. moves as “psychological warfare” and a “political game.”