The US president has taken a soft line on Turkey over its purchase of the S-400 system -- which was delivered on July 13 -- saying Thursday that he did not envisage sanctions "for now".

But Washington did respond by kicking Turkey out of its F-35 fighter jet programme -- a loss of billions of dollars for Turkish defence contractors.

The US says Russia could glean technical secrets about the new fighter jet if it is operated alongside the S-400.

"Trump does not want to impose sanctions on Turkey," said Cavusoglu in an interview with TV station TGRT Haber.

"When Trump promises something, he does his best to stick to it, but there are different points of view in the United States."

It is up to US lawmakers to decide on further punishing Turkey under the Countering America's Adversaries Through Sanctions Act (CAATSA), which prescribes penalties for countries that deal with Russia's defence sector.

But Cavusoglu said he expected Trump to waive any potential sanctions imposed by the US Congress.

"That is our expectation," he told TGRT Haber.

He also said exclusion from the F-35 programme could force Turkey to look elsewhere for new fighter jets.

"If the United States doesn't give us the F-35, while we are waiting to build our own planes... we will have to get them from another country, and no one can say anything about that," he said.

"We have the right to look at the options," he added, while insisting that Turkey would never leave the NATO alliance.