World governments reacted with concern after Turkey launched a military offensive on Kurdish forces in northern Syria, while the UN Security Council plans to hold an emergency meeting on the matter.
US President Donald Trump has defended his decision to pull US combat troops out of Syria – even as it triggered a Turkish-led ground attack – by saying the Kurds didn’t help the United States during WWII.
Around the world, governments have reacted with alarm as Turkey launched a full-scale offensive, including special forces and armoured units backed by a massive artillery bombardment and air support.
On Sunday, the Trump administration announced it was pulling troops out of northeast Syria, effectively paving the way for Turkish operations.
But on Thursday, Mr Trump defended the decision.
“The Kurds are fighting for their land… and as someone wrote in a very, very powerful article today, they didn’t help us with the Second World War, they didn’t help us with Normandy,” he told reporters at the White House.
“They mentioned names of different battles…in addition to that, we have spent a tremendous amount of money helping the Kurds, in terms of ammunition, in terms of weapons.
“That being said, we like the Kurds.”
However, Mr Trump called the Turkish incursion a "bad idea".
The president insisted Washington "does not endorse this attack", despite having withdrawn US troops from the area in what was interpreted as a green light for Turkey to assault Kurdish militias previously allied with America.
Earlier this week, Mr Trump said he would "obliterate" Turkey's economy if it went too far.
Before that, Mr Trump took to Twitter to defend the pull-out that led to the attack.
“But it is time for us to get out of these ridiculous Endless Wars, many of them tribal, and bring our soldiers home. WE WILL FIGHT WHERE IT IS TO OUR BENEFIT, AND ONLY FIGHT TO WIN,” he posted.
Australia has deep concerns
Senior federal government minister Greg Hunt has been careful not to comment on whether the Turkish offensive into Syria could spawn a potential return of the so-called Islamic State.
"We have deep and profound concerns," Mr Hunt told ABC Radio on Thursday.
Prime Minister Scott Morrison has defended Donald Trump over the contentious withdrawal of US troops, but would not be drawn on whether the US president's remarks on World War II are appropriate.
"Well, I'm not making a running commentary on what the President says and does, Mr Morrison told reporters.
In a follow-up statement, he said Australia was "deeply troubled" by Turkey's offensive.
"Actions of this nature will have grave consequences for regional security and could significantly undermine the gains made by the international coalition in its fight against Daesh," he said.
"It will cause additional civilian suffering, lead to greater population displacement and further inhibit humanitarian access."
'Act with restraint'
NATO chief Jens Stoltenberg urged Turkey to show "restraint" while acknowledging that Ankara had "legitimate security concerns."
"It's important to avoid actions that may further destabilise the region, escalate tensions, and cause more human suffering," Mr Stoltenberg said at a news conference in Rome.
The UN Security Council's president, South African ambassador Jerry Matthews Matjila, also appealed to Turkey to "protect civilians" and exercise "maximum restraint."
Ahead of the launch of the offensive, Russian President Vladimir Putin urged his Turkish counterpart Recep Tayyip Erdogan to "think carefully" before taking any action "so as not to harm overall efforts to resolve the Syrian crisis."
No funding for 'safe zone'
EU chief Jean-Claude Juncker demanded a halt to the operation, telling Ankara the bloc would not pay for any so-called "safe zone" that might be created.
He told the European Parliament he recognised Turkey had "security concerns" along the border. But he warned that the military action would not lead to a "good result", saying a political solution was the only way to end the Syrian conflict.
'Risk of resurgent IS'
Turkey "is willingly risking further destabilising the region and a resurgence of IS" by attacking northeastern Syria, German Foreign Minister Heiko Maas said.
"Syria needs stability and a political process... however, the Turkish offensive now threatens to cause a new humanitarian disaster," Mr Maas said in a statement, adding that Berlin would "urge Turkey to end its offensive and to pursue its security interests peacefully."
French Foreign Minister Jean-Yves Le Drian said the offensive "must stop".
"It calls into question the security and humanitarian efforts of the coalition against Daesh and risks undermining Europeans' security," he said in a tweet, using the Arabic name for the Islamic State (IS) group.
French European Affairs Minister Amelie de Montchalin earlier said France, Germany and Britain were working on a joint declaration "which will be extremely clear on the fact that we very strongly condemn" the Turkish campaign.
'Risks destabilising the region'
British Foreign Secretary Dominic Raab expressed "serious concerns about the unilateral military action that Turkey has taken".
The action "risks destabilising the region, exacerbating humanitarian suffering, and undermining the progress made against Daesh which should be our collective focus," he added in a statement.
Dutch Foreign Minister Stef Blok said he had summoned Turkey's ambassador to condemn the assault.
"I call on Turkey not to follow the path it has chosen," he said.
"No one can benefit from the potentially terrible humanitarian consequences. The operation can trigger new refugee flows and harm the fight against IS and stability in the region."
Already struggling population
The International Committee of the Red Cross said it was "deeply concerned that any escalation in the country’s north-east could harm an already struggling population," stressing that "the humanitarian space" needs to be preserved".
With additional reporting from wires