Turkish President Recep Tayyip Erdogan on Monday threatened to thwart the creation of a new US-backed 30,000-strong border security force in northern Syria before it was even set up.

"America has acknowledged it is in the process of creating a terror army on our border. What we have to do is nip this terror army in the bud," Erdogan said in a televised speech outside Ankara.

Turkish officials objected earlier that the new force would be comprised of the Kurdish People's Protection Units (YPG) militia Ankara accuses of being terrorists.

The YPG played a a key role in the Syrian Democratic Forces (SDF) alliance that last year ousted Islamic State jihadists from their stronghold of Raqa in northern Syria.

American officials said at the weekend that the new force was needed as the focus shifted from fighting IS extremists to border security in northern Syria.

The new upsurge of tensions between Ankara and Washington comes as Erdogan repeatedly threatens that Turkey could launch a cross-border operation to oust the YPG from the Kurdish-held town of Afrin in northern Syria.

Erdogan on Monday reaffirmed again that the Turkish army was ready "at any moment" to launch an operation against the YPG in Syria.

"The preparations have been completed, the operation could start at any moment," said Erdogan.

Turkey accuses the YPG of merely being the Syrian offshot of the Kurdistan Workers Party (PKK) which has waged an over three-decade rebellion in the Turkish southeast and is regarded as a terror group by Ankara and its Western allies.

Deputy Prime Minister and government spokesman Bekir Bozdag warned the United States on Twitter it was "playing with fire" and its actions were "not compatible with friendship, alliance or a strategic partnership".

Source: AFP