ISTANBUL (REUTERS) - Turkey's president Tayyip Erdogan said Washington was not right to propose that Ankara get rid of the Russian S-400 missile defences it purchased, calling it an infringement of sovereign rights, according to Turkish media.

In a meeting at the White House on Wednesday, US President Donald Trump urged Erdogan to abandon the S-400 systems that began arriving in Turkey in July despite threats of sanctions from Washington.

Asked after his meeting whether Turkey would consider not activating the S-400s, Erdogan told reporters Ankara cannot harm its relations with Russia.

He also again held out the option of buying US Patriot defences.

"We said, 'We see the proposal to remove the S-400s completely while buying the Patriots as an infringement of our sovereign right and certainly do not find it right,'" he was quoted as saying by broadcasters.

"This is the most binding element: we have some strategic efforts with Russia," Erdogan said, adding the Turkstream natural gas pipeline, which begins in Russia and runs through Turkey, will start delivering gas to Europe.

"I cannot abandon the S-400s because of Patriots now. If you are going to give us Patriots, give them," he was quoted as saying.

Largely thanks to good relations between the two presidents, Turkey has so far avoided US sanctions that by law should be triggered by the S-400s.

But the United States has banned sales of F-35 fighter jets to Ankara and removed it from a multinational programme to produce the warplane.

Erdogan said that he saw a much more positive approach to the F-35 issue from Trump.