A US Navy warship believed to be carrying Marines and sailors to the Middle East is nearing the Malacca Strait off Singapore as it makes its way to the region, maritime tracking data showed Tuesday.

The amphibious assault ship USS Tripoli was approaching Singapore, at the southwestern edge of the South China Sea, Tuesday morning, according to AIS tracking data seen by CNN.

US Navy ships often move with AIS transponders turned off. Revealing their positions while transiting areas with heavy maritime traffic, like the waters around Singapore, enables safer operations.