Turkey's air and ground offensive in northwest Syria's Afrin region against the Kurdish YPG militia has opened a new front in the seven-year, multi-sided Syrian civil war and strained ties with NATO ally Washington.
Ankara views the YPG as terrorists and as an extension of the outlawed Kurdistan Workers Party (PKK) and has been infuriated by US support, including arms and training, for the militia. The Kurdish fighters have played a prominent role in US-led efforts to combat the hardline Islamic State in Syria.
Since the start of the eight-day-old incursion, dubbed "Operation Olive Branch" by Ankara, President Tayyip Erdogan has said Turkish forces would push east towards the town of Manbij, potentially putting them in confrontation with US troops deployed there.
US National Security Adviser H.R. McMaster told Erdogan's spokesman, Ibrahim Kalin, in a telephone call that the United States would no longer provide weapons to the YPG, the Turkish presidency said on Saturday.
"It was emphasised that Turkey's legitimate security concerns must be paid attention to. It was agreed that close coordination would be carried out in order to avoid misunderstandings," it said.
The agreement is likely to be seen by Ankara as a substantial diplomatic victory from the incursion, where Turkish troops and their Syrian rebel allies appear to have made modest advances, as heavy rain and poor weather have hampered air strikes and progress on the ground.
Turkey's foreign minister said the United States needed to follow up its promise with concrete action, including the immediate withdrawal of its troops from the vicinity of Manbij.
"The United States needs to break its link with (the) terrorist organisation and make them drop their weapons completely. They need to collect the weapons they gave, they need to withdraw from Manbij immediately," Mevlut Cavusoglu told reporters on Saturday.
The US State Department did not immediately respond to requests for comment about ending arms to the YPG or exiting Manbij.
Erdogan looks east
Erdogan said this week that Turkish forces would sweep Kurdish fighters from the length of Syrian border and could push all the way east to the frontier with Iraq, a move that would risk a possible confrontation with US forces allied to the Kurds.
Any drive by Turkish forces toward Manbij, part of Kurdish-held territory some 100 km (60 miles) east of Afrin, could also threaten US efforts to stabilise northern Syria. The United States has about 2,000 troops in Syria, officially as part of the international coalition against Islamic State.
US forces were deployed in and around Manbij to deter Turkish and US-backed rebels from attacking each other and have also carried out training missions in the area.
A senior official for the US-backed Syrian Democratic Forces (SDF), an alliance of Syrian fighters spearheaded by the Kurdish YPG, said any wider Turkish assault would face an "appropriate response".
Redur Xelil also said in an interview that he was sure the US-led coalition against Islamic State, which has backed the SDF in its battle against the jihadists, was trying to put pressure on Turkey to limit its offensive.
Turkey and its Free Syrian Army (FSA) rebel allies have killed a total of 394 militants since the incursion began, Erdogan said on Saturday. Turkey and the FSA rebel factions have together lost 20 people he said, without giving a breakdown.
The SDF has accused Turkey of exaggerating the number of Kurdish fighters it had killed.
The Syrian Observatory for Human Rights, a Britain-based war monitoring group, said that 36 civilians in Afrin, including 10 children, have died so far.
A total of 59 YPG fighters and at least 69 fighters from the Turkey-backed FSA have died in clashed, the Observatory said. Seven Turkish soldiers have been killed and another seven are missing, it said.