U.S. National Security Adviser John Bolton was set to depart Turkey on Tuesday without meeting President Recep Tayyip Erdogan, in an apparent snub over disagreements about Kurdish fighters in Syria. A U.S. official had said over the weekend that the two were expected to have consultations on Tuesday about the fate of Kurds allied with the United States in Syria as part of discussions about President Donald Trump's troop draw-down from the country.

National Security Council spokesman Garrett Marquis said U.S. officials were told Erdogan cited local election season and a speech to parliament for not meeting with Bolton.

In the speech to parliament Tuesday, Erdogan criticized the U.S. position that the Kurds must be protected, reiterating his government's position that they are a terrorist group.

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Turkey "cannot make any concessions"

Erdogan said Turkey's preparations for a new military offensive against what he called the terror groups in Syria were, "to a large extent" complete.

Erdogan made the comments just hours after Bolton met with Turkish officials seeking assurances that Turkey won't attack the U.S-allied Kurdish militiamen and women in Syria.

Turkey's President Recep Tayyip Erdogan gestures as he delivers a speech to MPs of his ruling Justice and Development Party (AKP) at the parliament in Ankara, Turkey, Jan. 8, 2019. AP

Erdogan called Bolton's remarks that the Kurds' safety must be guaranteed "unacceptable," and said Ankara "cannot make any concessions. Those involved in a terror corridor (in Syria) will receive the necessary punishment."

Turkey insists its military actions are aimed at Kurdish fighters in Syria whom it regards as terrorists and not against the Kurdish people.

Why the Kurds' fate matters to the U.S.

President Trump stunned U.S. allies and lawmakers on both sides of the aisle in Washington last month when he announced that ISIS was defeated and all 2,000 American troops in Syria were, "coming back now."

Bolton's remarks over the weekend, hinging the U.S. withdrawal on a final defeat of ISIS and security for the Kurdish fighters, dramatically shifted the White House policy.

Although Mr. Trump insisted on Monday that he hadn't changed his mind about pulling troops out of Syria, CBS News senior national security correspondent David Martin reported that the new withdrawal timetable is dramatically different: When Mr. Trump first made the announcement it was 30 days, then it stretched to 120, but with Bolton's remarks it was clear the commitment had become open-ended.

Erdogan's refusal to bow to U.S. pressure on the Kurdish fighters all but obligates Mr. Trump to leave American troops in northern Syria, alongside their partners, as a buffer against any Turkish aggression.

And as Martin reported, the fighting continues on the ground as the U.S. backed forces close in on the last ISIS strongholds in Syria. In the course of that fight, the Kurds recently captured an American citizen, Warren Christopher Clark, a Houston resident who joined the Islamic extremists.

Clark is now one of more than 700 captured foreign fighters held by U.S.-backed forces in Syria.

If the U.S. were to pull out of Syria abruptly, Martin says all those fighters would almost certainly be released, and able to return to the battlefield.