Turkish President Recep Tayyip Erdogan has said he will tell President Barack Obama that US weapons have helped Syrian Kurds, blamed by Turkey for Wednesday’s Ankara bombing.
He said he had no doubt the Syrian PYD and its military wing were behind the rush-hour blast which killed 28 people.
The bombing came as Syrian Kurds threatened to extend their control of territory along Turkey’s border.
The US backs the PYD in the fight against so-called Islamic State (IS).
And yet it sees the Kurdish militant PKK inside Turkey as a terrorist organisation, even though it is affiliated to the PYD and its military arm, the People’s Protection Units (YPG).
Continued American support for Syrian Kurds, reiterated by a state department spokesman this week, is threatening to cause a rift between the two Nato allies.
Mr Erdogan told reporters there was “no doubt about the fact that those who carried out this attack are the YPG and the PYD”.
He planned to tell Mr Obama later on Friday over the phone to consider “how and where those weapons you provided were fired”.,
Turkey has already named the man who detonated the Ankara bomb as Salih Necar, a Syrian national and member of the YPG.
A convoy of five military vehicles were targeted as they passed close to government offices while workers were going home.
The PYD has denied involvement in the attack and the US has said it is unable to confirm or deny the Turkish allegation.
Mr Erdogan said he was saddened by the West’s reluctance not to link the YPG to the Turkish-based Kurdistan Workers’ Party, viewed as a terror group by both the EU and the United States.
He pointed out that he had told President Obama months before that after three plane-loads of US weapons arrived, half ended up in the hands of fighters of so-called Islamic State and the rest with the PYD.
“They were used against civilians there and caused their deaths,” he complained.
The Turkish leader appeared to refer to a US air drop of military supplies in late 2014 meant for Iraqi Kurdish forces during the battle for the town of Kobane, Reuters reported.
As the Syrian army, backed by Russian air power, has targeted Syrian opposition forces and pushed further north in Aleppo province, the Syrian Kurdish militia has made gains from the rebels close to the Turkish border.
Turkey fears they could seize a 100km-stretch (62 miles) as far as Jarablus to create a large zone along the border.
The army has continued to shell YPG targets across the border near the rebel-held town of Azaz.
Turkey also has concerns that the PKK is being given support by the Syrian Kurdish militia in its battle with security forces in south-east Turkey.
“There’s close integration and there’s talk of tunnels for the flow of weapons,” Burhanettin Duran of the pro-government Seta research institute told the BBC.