A tweet from the State Department spokesman:
PJCrowley Philip J. Crowley
We have been in touch with the #Japanese government and we stand ready to provide whatever assistance needed in response to the #tsunami.
Adding to the unfolding chaos is another concern, that of the global markets. Already affected by spiralling oil and food prices, there are fears the Japan earthquake will hit Asian markets and those beyond.
So far Japanese stock futures have fallen 3.3 per cent, but the yen currency has recovered from an initial dip in the day.
Major southeastern Asian stock markets have also fallen more than one per cent in the wake of the disaster.
In Europe the insurance section has lost out due to worries over the prospect of claims from the earthquake. However analysts are saying it is too early to tell what the wider or long term effects will be.
Barack Obama, the US president, has offered his condolences to the people of Japan.
"Michelle [Obama] and I send our deepest condolences to the people of Japan, particularly those who have lost loved ones in the earthquake and tsunamis," he said in a statement on Friday.
The president said he would monitor the tsunami triggered by the massive quake, and urged citizens in places expected to be affected to listen to their local authorities.
A tsunami is expected to reach Hawaii within the next few hours.
Steff Gaulter, Al Jazeera's senior meteorologist has been explaining the scale of the tsunami effect across the Pacific Rim.
She said the lack of friction in the sea means there's nothing to slow the waves down.
"Say you have a little toy, you push it along a desk, it will eventually stop - friction will slow it down. But in the sea there's not a great deal there so the waves will just keep going.
"Also these waves travel incredibly fast - we're talking about 12 hours to get to the north island of New Zealand. Flying from Japan to New Zealand wouldn't take much less than that."
Gavin Blair, a freelance journalist in Tokyo, has told Al Jazeera of the moment the earthquake was felt in the city.
I was on the ground floor of a building in Tokyo that began to shake, gently at first and then vigorously. Some people were going out into the streets, others were going under tables.
"The aftershocks were still hitting us three hours later," he said, adding it was the biggest quake he had felt in 14 years.
Blair said regular quake drills and quake-proofed buildings have definitely helped save lives in the country, but that there was little authorities could do in the face of the tsunami.
Why Japan is prone to earthquakes: Al Jazeera's senior meteorologist, Steff Gaulter, gives her expert insight:
More now on the Fukushima nuclear plant affected by the earthquake: Japan has issued at state of emergency at the plant after a cooling system failure. Authorities say there is no radiation leak but they are having trouble cooling the plant.
Earlier a fire was reported in the turbine building of the plant in Miyagi prefecture.
Step Vaessen, Al Jazeera's correspondent in Jakarta, said the Indonesian province of Papua is expected to be hit by a small tsunami not higher than 80cm high within the next 30 minutes.
"In the last hour they [authorities] have worked really hard to make sure people have been evacuated from the beaches," she said.
Just to put that height in perspective - the devastating tsunami of December 2004 saw waves 10-15m high hit the coast of Sumatra.
Back to the tsunami warning, New Zealand has now issued its own warning for the country and has warned people to stay clear of beaches.
The Civil Defence said waves less than one metre in height were expected at the coastline.
In Taiwan authorities have said small tsunamis have hit their coastline without causing any damage. However the country has kept its tsunami warning in place.
For scenes from the moment the quake struck, check out this report from Al Jazeera's Laurence Lee: