BRUSSELS — US concerns over the European Union’s (EU) landmark defense cooperation pact and increasingly strained relations between Washington and Turkey look set to loom large as North Atlantic Treaty Organization (NATO) defense ministers meet for talks on Wednesday.

The US and Ankara, two of the transatlantic alliance’s most important members, are at loggerheads over Turkey’s military offensive in northern Syria, which US Secretary of State Rex W. Tillerson on Tuesday warned was detracting from the fight against the Islamic State group.

The two-day meeting at NATO headquarters in Brussels is expected to approve changes to NATO’s command structure aimed at making the alliance fit for the challenges of warfare in the 21st century, particularly cyber tactics and hybrid warfare, as fears grow about Russian assertiveness.

But a working dinner with EU diplomatic chief Federica Mogherini on Wednesday night has taken on greater significance after senior US officials voiced fears about the bloc’s defense pact and NATO Secretary-General Jens Stoltenberg warned it must not undermine the alliance.

Mr. Stoltenberg said Tuesday that efforts to boost EU defense spending were welcome, but only if they were coordinated with NATO plans, warning there was “no way” the EU could replace the transatlantic alliance in guaranteeing European security.

“It will be absolutely without any meaning if NATO and the EU start to compete,” the former Norwegian premier told reporters.

“European allies are absolutely aware that the defence, the protection of Europe is dependent on NATO.”

The EU’s so-called permanent structured cooperation on defense agreement, known as PESCO, has projects in view already to develop new military equipment and improve cooperation and decision making.

But on Sunday a senior official working with US Defense Secretary Jim Mattis said Washington had concerns some of the proposed initiatives risked “pulling resources or capabilities away from NATO.”

And on Tuesday US ambassador to NATO Kay Bailey Hutchison ramped up the pressure, warning the EU there could be serious consequences if it shuts US defense companies out of cooperation projects.

“Certainly we do not want this to be a protectionist vehicle for the EU and we’re going to watch carefully, because if that becomes the case then it could splinter the strong security alliance that we have,” she told reporters.

The US concerns have surprised some European diplomats, with one insisting that EU defense cooperation poses no threat to NATO, adding that “a little explanatory work” is required to clarify matters with the Americans.

Wednesday’s dinner now represents an important chance for Ms. Mogherini to reassure the US, which is NATO’s biggest contributor. — AFP