US politicians pressured the Trump administration to impose sanctions on Turkey for the purchase of a Russian missile defense system, saying that failing to do so sends a "terrible signal."
A key Senate committee will vote on additional legislation to punish Ankara this week.
"The time of patience has expired a long time ago. It is time for them to apply the law," Democratic Senator Chris Van Hollen and Republican Senator Lindsey Graham said in a letter to Secretary of State Mike Pompeo.
"Not doing so is sending a terrible signal to other countries that they can ignore US laws without consequences," they said.
Ankara and Washington have disagreed over Turkey's purchase of the NATO ally of the Russian S-400 missile system, which Washington says is not compatible with NATO's defenses and poses a threat to its stealth fighter jets F -35, which Lockheed Martin Corp is developing.
Enraging many members of Congress, Turkey ignored the threat of US sanctions and began receiving its first S-400 deliveries in July. In response, Washington withdrew Turkey from the F-35 program.
The administration of the president of the United States, Donald Trump, has delayed the imposition of sanctions even though Trump signed a radical sanctions law, known as CAATSA, in 2017. Establishes financial sanctions for countries that do business with the army of Russia.
The anger of US politicians towards Turkey intensified after Ankara crossed into Syria over an offensive against Kurdish fighters who had helped US forces fight the armed group ISIL (ISIS).
Senator Jim Risch, Republican president of the Foreign Relations Committee, told reporters that the committee will vote next week on a separate bill to impose severe sanctions on Ankara.
S-400 missile system
Normally fervent defenders of Republican Trump, Graham and some other party members have strongly criticized the president's decision to withdraw troops from northeastern Syria, paving the way for the Turkish military operation against Kurdish fighters.
Trump received Turkish President Recep Tayyip Erdogan at the White House for a meeting last month, which the US leader described as "wonderful."
But there have been no signs that Erdogan has changed his plan to buy the Russian system.
Turkey's presidential administration has said that the date of purchase of more Russian S-400 missile systems is just a technicality, and believes that an agreement will happen in a short time, the RIA news agency reported on Monday.
The State Department did not respond to a request for comment. Pompeo said on November 26 that Turkey carrying out tests on the Russian system was "worrisome,quot;, and that the talks to solve the problem were still ongoing.
On the same day, Russia's state arms exporter, Rosoboronexport, was quoted as saying that Moscow hoped to seal an agreement to supply Turkey with more S-400 missile systems in the first half of 2020.