WASHINGTON, July 18 (Xinhua) -- U.S. President Donald Trump on Thursday sent contradictory messages on whether the United States would impose sanctions against Turkey over its purchase of Russian S-400 air defense system.

"No ... We're not looking at that right now," Trump replied to reporters in the Oval Office when asked if there will be sanctions on Turkey, which began taking the delivery of the Russian S-400 system Friday.

Trump, however, later clarified his previous comments during his meeting with the visiting Dutch Prime Minister Mark Rutte. "We're looking at it and see what we do. We haven't announced that yet," he said.

He also blamed the "very difficult situation" on the Obama administration. "The previous administration made some very big mistakes with regard to Turkey and it was too bad," he added.

The White House and the Pentagon confirmed on Wednesday that Turkey's purchase of S-400 systems had led to the termination of Ankara's involvement with the F-35 program. The Trump administration, at the same time, sought to reduce the repercussion for the bilateral relations.

A statement issued by the White House on Wednesday made no mention of possible sanctions against Turkey as required by law under the Countering America's Adversaries Through Sanctions Act (CAATSA).

Pentagon officials also deferred all questions about possible sanctions to the Department of State.

U.S. lawmakers and some senior officials have expressed full support to slap sanctions on Turkey.

In a letter published last week, bipartisan senators urged the Trump administration to fully implement sanctions under the CAATSA. Secretary of State Mike Pompeo also suggested in a Sunday interview that the sanctions against Ankara might be imminent.

"The law requires that there be sanctions and I'm confident that we will comply with the law and President Trump will comply with the law," he said.

Turkish Foreign Ministry on Wednesday called the U.S. move to terminate Turkey's participation in the F-35 program illegitimate and might bring irreparable damage to bilateral relations.