The United States will send extra military aircraft to Australia’s tropical north this year, a U.S. Marine Corps spokesman said on Wednesday, bolstering its military presence close to the disputed South China Sea.

The Marines’ deployment in the strategic city of Darwin, agreed in 2011, was a critical part of former U.S. President Barack Obama’s “pivot” to Asia amid China’s increased assertiveness in the region.

The move also cemented close ties with staunch ally Australia and gave the U.S. a foothold in the area.

President Donald Trump’s new administration has struck a hawkish tone over Chinese territorial claims in the South China Sea Asia, but it has abandoned the Trans-Pacific Partnership trade pact negotiated by Obama.

Marine Corps spokesman Major Chris Logan said there would be an increase in aircraft this year, including sending four MV-22 Osprey tilt-rotor planes, which boost the range of the Marine force and five AH-1W Super Cobra helicopters.

Logan added that Marine numbers would remain at 1,250.

“The size and composition of each Marine rotation to Australia is mutually determined … and is balanced against other resource commitments and respective national priorities,” Logan said.