Donald Trump is “fully prepared” to use military force if “needed” against Turkey after Ankara launched an offensive against America’s allies in Syria.
“We prefer peace to war,” Secretary of State Mike Pompeo told CNBC.
“But in the event that kinetic action or military action is needed, you should know that President Trump is fully prepared to undertake that action.”
He declined to say where Mr Trump’s red line would be to prompt a US military response, and the State Department refused to comment.
The comments from the president’s top diplomat came as skirmishes between Turkish and Kurdish forces continued despite a five-day ceasefire brokered by the US, which is due to end on Tuesday.
Mr Trump said the ceasefire was holding, dismissing the clashes.
The president has been criticised by Democrats and Republicans for suddenly announcing he was withdrawing US troops from Syria, leaving their allies, the Kurds, to fend off Turkey who sees them as being linked to terrorists.
On Monday he announced not all troops would be leaving straight away, despite saying he did not want to leave any in Syria.
He said some troops would remain in the country and others currently in Syria would be redeployed to Iraq instead of going home.
Speaking at a meeting with his cabinet, Mr Trump said: “We never agreed to protect the Kurds for the rest of their lives.”
He added that he was achieving a campaign promise to disengage from international conflicts as he looks ahead to next year’s election.
The president said a small number of US troops would stay “in a little different section to secure the oil,” as well as in “a totally different section of Syria near Jordan and close to Israel”.
“That’s a totally different mindset,” he said.
“Other than that, there’s no reason for US troops to remain. They’re going to be sent initially to different parts.
“Ultimately, we’re bringing them home.”
He added that Israel and Jordan asked him to keep some troops in Syria.
US defence secretary Mark Esper said the Pentagon was considering keeping some US troops near oilfields in northeastern Syria alongside Kurdish-led Syrian Democratic Forces (SDF) to ensure Islamic State (IS) militants cannot get to the oil.
As the ceasefire comes to an end, Germany suggested a security zone in northern Syria was created to protect displaced civilians and ensure the fight against IS insurgents continues.
German defence minister Annegret Kramp-Karrenbauer said the zone should involve Turkey and Russia to protect at least 160,000 Syrian Kurds who the UN says have fled their homes since the Turkish assault started.
It is the first time the German government has proposed a military mission in the Middle East, with Berlin expected to send soldiers to Syria if it is backed by Turkey and Russia, who see the Kurds as enemies.
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