Another powerful typhoon has formed in the Pacific and is bearing down on the Northern Mariana Islands near Guam, even as a super typhoon is threatening havoc on the Philippines.

Typhoon Melor was about 490km east of the US territory of Guam late on Friday and was tracking northwest towards the Marianas where it was expected to slam the tiny islands at the weekend at near top intensity, according to the US Navy's Joint Typhoon Warning Centre.

Melor "is expected to cross the island chain... at near super typhoon intensity", bringing with it open-water waves of more than eight metres, JTWC said in a briefing.

The storm was packing sustained winds of 225km/h on Friday and was expected to strengthen over the next 24 hours and reach 258km/h by Sunday.

A typhoon warning is in effect for the Mariana islands of Saipan and Tinian, while Guam is under a tropical storm warning.

US aid officials said they have advance personnel teams in place in Guam, just south of the Marianas, and are prepared to use pre-positioned supplies there and in the US-administered Northern Mariana Islands in the event of a disaster.

"Typhoon Melor is forecast to strengthen and become a super typhoon," Federal Emergency Management Agency chief Craig Fugate told reporters in Washington.

"We are prepared to support the Northern Mariana Islands and Guam if they are struck."

Meanwhile millions of terrified flood survivors in the disaster-struck Philippines hunkered down on Friday as super typhoon Parma, packing gusts of 230km/h, was forecast to slam rural areas in the north of the main island Luzon before dawn on Saturday.