WASHINGTON, Nov. 26 (Xinhua) -- The delegation of the United States will highlight the progress on burden sharing, security and defense cooperation as well as the future development of the North Atlantic Treaty Organization (NATO) during the upcoming NATO summit, said the U.S. State Department on Tuesday.

U.S. Secretary of State Mike Pompeo will join the U.S. delegation led by President Donald Trump to attend the NATO Leaders Meeting on Dec. 3-4, the State Department said in a statement.

The leaders of NATO members will gather to commemorate the alliance's 70th anniversary in London next week, while the bloc's unity has been widely questioned.

The Trump administration has repeatedly complained about NATO allies' free-riding on the U.S. military. Besides, there are disagreements within the alliance over the Iran nuclear issue, Turkey's operations in northern Syria as well as the Nord Stream 2 pipeline project between Germany and Russia.

French President Emmanuel Macron said in a recent interview that the alliance was experiencing "brain death," triggering a backlash from Trump and Turkish President Recep Tayyip Erdogan.