"We're not looking at that right now," Trump told reporters.

Speaking shortly afterward, he seemed to clarify: "We're looking at it. Very, very difficult situation for a lot of reasons."

"We'll see what we do. We haven't announced that yet," he said.

The United States said Wednesday that it was booting Turkey from its signature F-35 stealth fighter jet program after it defied warnings and began delivery of the S-400 missile defense system.

Under a 2017 law approved by Congress, the United States is also required to impose sanctions over individuals involved in "significant" arms deals with Russia.

"Things could have been done better in the previous administration. It was bad," Trump said.

Trump last month met Turkish President Recep Tayyip Erdogan and appeared to be sympathetic to his case.

Erdogan told Trump that he went ahead because previous president Barack Obama did not allow Turkey to buy the rival US Patriot system.

In fact, Turkey in 2013 had picked a Chinese-made air defense system over the Patriots, citing its lower cost, but the deal collapsed.

US officials worry that the purchase of the S-400 will allow Russia to hone the system's ability to shoot down Western planes due to Turkey's role in the NATO alliance.