LONDON, May 20 (Reuters) - Iran called on Monday on the United States to address the Islamic Republic with respect, not threat of war, a day after U.S. President Donald Trump threatened Tehran in a tweet, raising concerns about a potential U.S.-Iran conflict.

Tensions between Washington and its Gulf Arab allies on one side and Tehran and its proxies in the region on the other, have been flaring for weeks.

On Sunday, Trump tweeted: "If Iran wants to fight, that will be the official end of Iran. Never threaten the United States again!"

Iranian Foreign Minister Mohammad Javad Zarif replied on his twitter account "NeverThreatenAnIranian. Try respect—it works!"

Zarif, who was educated in the United States, actually praised Trump for earlier remarks seen as pushing back against hawks in his administration who were encouraging conflict. The president "rightly deplores 'military-industrial complex' pushing U.S. #ForeverWars," Zarif wrote on Twitter.

But he said Trump had allowed a "B-team" of aides led by National Security Advisor John Bolton to "trash diplomacy." He accused them of "milking despotic butchers via massive arms sales," an apparent reference to Iran's main regional foe, Saudi Arabia, Washington's biggest arms buyer.

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."

Britain told Iran on Monday not to underestimate the resolve of the United States, warning that if American interests were attacked then the Trump administration would retaliate.

The foreign minister of Oman, which in the past helped pave the way for negotiations between Iran and the United States, visited Tehran on Monday.

Yousuf bin Alawi bin Abdullah discussed regional and international issues with Zarif, Iranian state news agency IRNA said. It gave no further details. (Reporting by Bozorgmehr Sharafedin Editing by Peter Graff)