Typhoon Mawar packing potentially catastrophic winds was heading Wednesday for a direct hit on Guam, a US territory in the Pacific that is a crucial American military outpost.

A National Weather Service (NWS) report said Mawar's top winds had weakened slightly but remained a dangerous Category Four typhoon with maximum sustained winds of 140 miles (225 kilometers) per hour, and gusts up to 175 mph at landfall.

Mawar dropped from super typhoon status when its sustained winds fell below 150 mph but the NWS in Guam reported that the typhoon "may strengthen slightly on approach to Guam."

On its current trajectory, Mawar will smash into the island of 170,000 people, unleashing torrential rains and extreme flooding.

As of 8:00 am Wednesday Guam time (2200 GMT Tuesday), the storm was 75 miles southeast of Guam, the NWS said in an advisory. Maximum winds on the island were expected at around 5:00 pm local time, it said.