LONDON (Reuters) - U.S. Defence Secretary Mark Esper urged Turkey on Monday to stop holding up support for a NATO defence plan for the Baltics and Poland, as Ankara presses the alliance to support its fight against U.S.-backed Kurdish YPG militia in Syria.

FILE PHOTO: U.S. Defense Secretary Mark T. Esper delivers remarks before ringing the closing NASDAQ bell for Veterans Day in New York, New York, November 11, 2019. Picture taken November 11, 2019. DoD/Lisa Ferdinando/Handout via REUTERS/File Photo

In an interview with Reuters ahead of the NATO summit, Esper warned Ankara that “not everybody sees the threats that they see” and added he would not support labelling the YPG as terrorists to break the impasse.

He called on Ankara to focus on the larger challenges facing the North Atlantic Treaty Organization.

“The message to Turkey ... is we need to move forward on these response plans and it can’t be held up by their own particular concerns,” Esper said as he flew to London.

“Alliance unity, alliance readiness, means that you focus on the bigger issues – the bigger issue being the readiness of the (NATO) alliance. And not everybody’s willing to sign up to their agenda. Not everybody sees the threats that they see.”

NATO envoys need formal approval by all 29 members for the plan to improve the defence of Poland, Lithuania, Latvia and Estonia against any threat from neighbouring Russia.

The dispute, as NATO prepares to hold its 70th anniversary summit, is a sign of deep divisions between Ankara and Washington over everything from the war in Syria to Turkey’s growing defence relationship with Russia.

Turkey wants NATO to formally recognise the YPG militia, the main component of the U.S.-backed Syrian Democratic Forces (SDF), as terrorists and is infuriated that its allies have given the militia support.

Ankara has blamed Washington for the current impasse, saying it was caused by the U.S. withdrawal of support from a separate defence plan for Turkey, covering any possible attack from the south where it borders Syria.

Asked whether Washington might agree to branding the YPG as terrorists in order to break the deadlock, Esper said: “I wouldn’t support that.”

“We’re going to stick to our positions, and I think NATO will as well,” Esper said.

The issue is the latest source of friction between the NATO allies, which have also been at loggerheads over Turkey's purchase of advanced Russian air defences, which Washington says are incompatible with NATO defences and pose a threat to Lockheed Martin Corp's LMT.N F-35 stealth fighter jets.

Washington said in July it was removing Turkey from the F-35 program and has warned of possible U.S. sanctions.

Two U.S. senators pressed the Trump administration on Monday to impose sanctions on Turkey over its purchase of the Russian missile defence system and said the failure to do so sent a “terrible signal.”