Strong winds and heavy rain have begun buffetting Guam as Typhoon Dolphin inches slowly towards the island.
Meteorolgists say the typhoon, with winds of up to 180 kilometres an hour at its centre, has stalled off the island's east coast, which could give it a chance to build strength.
A meteorologist with the US National Weather Service on Guam, Mike Middlebrook, says the typhoon was originally expected to pass between Guam and the Northern Marianas island of Rota to the north.
But now he says it's possible Guam could be in for a direct hit later this evening.
"Right now it seems to be stalled. In the last hour or so it's moved very little, so we're waiting to see what direction it decides to go. But in the meantime, Guam is getting some very heavy rain and near typhoon-force winds. If it decides to say, for example, drift slowly west all night we could really catch it here on Guam with a prolonged period of destructive winds."
Mike Middlebrook says Dolphin is looking to be the strongest typhoon since Pongsona in 2002.
Evacuation centres have been set up in both Guam and the Northern Marianas, schools and businesses closed, and authorities are urging people to stay indoors.