Erdogan previously said Turkey and Russia could work together to solve the conflict.

The law requires foreign social media sites to appoint Turkish-based representatives to address authorities' concerns over content and includes deadlines for removal of material they take exception to.

It was unclear what specific invitation Erdogan was referring to as the interior minister in the Tripoli-based government, Fathi Bashagha, suggested in comments to reporters in Tunis that no official request had yet been made.

The Turkish president told reporters he might be persuaded to use the U.S.-made Patriot system "as well'' as the Russian S-400. Trump said they would agree to keep working on the issue.

"I have worked hard to solve some of your problems. Don't let the world down. You can make a great deal," said Trump in the letter.

On Sunday, Trump said he was listening to Congress, where Republicans and Democrats are pushing aggressively for sanctions action.

Imamoglu narrowly won a previous mayoral election on March 31, but Erdogan's Justice and Development Party challenged the vote.

Turkey President Tayyip Erdogan also appeared to concede defeat in the country's largest city, Istanbul.

Turkish President Tayyip Erdogan on Monday described a mass shooting which killed 50 people at two New Zealand mosques as part of a wider attack on Turkey and threatened to send back "in caskets" anyone who tried to take the battle to Istanbul.

Saudi officials murdered journalist Jamal Khashoggi in their Istanbul consulate after plotting his death for days, Turkey’s president said.