US President Donald Trump is said to have told the Turkish president, Recep Tayyip Erdoğan, that the US will no longer supply arms to the Syrian Kurdish fighter groups known as People's Protection Units or YPG.

Turkey considers the YPG to be terrorists because of their affiliation to outlawed Kurdish rebels who have been waging an insurgency in Turkey for 30 years.

The issue was addressed in a news conference by Turkish Foreign Minister Mevlüt Çavuşoğlu.

"One subject that negatively impacts our relationship with America is the weapons that the US has given to the YPG (People's Protection Units - Kurdish Syrian fighters)," Mr Çavuşoğlu told reporters.

"Our esteemed president, Recep Tayyip Erdogan, once again reiterated his discomfort to Mr. Trump. Mr. Trump clearly stated that he had given clear instructions and that the YPG won't be given arms and that this nonsense should have ended a long time ago."

But the announcement has come as a surprise to US officials.

The YPG were a key US ally against the Islamic State group in Syria.

Officials at the Pentagon and US State Department, who would normally be informed of such a change, said they were unaware of any changes.