Master Chief David Unnone (C), of the US 7th Fleet command ship USS Blue Ridge (LCC 19), briefs sailors about taking on humanitarian assistance supplies in Singapore as part of preparatory efforts if directed to support earthquake and tsunami relief operations in Japan, in this photograph taken and released on March 11, 2011. [Photo/Agencies]

WASHINGTON - President Barack Obama sent condolences to the people of Japan on Friday and said the United States would provide any help its close ally needed after a massive earthquake and tsunami killed hundreds.

The Defense Department was preparing American forces in the Pacific Ocean to provide relief after the quake, which generated a tsunami that headed across the Pacific past Hawaii and toward the west coast of the US mainland.

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Authorities said hundreds of people were killed in Japan and the toll was expected to surpass 1,000.

Obama was awakened by his chief of staff, Bill Daley, at about 4 am EST (0900 GMT) and called Japanese Prime Minister Naoto Kan later in the morning.

"On behalf of the American people, I conveyed our deepest condolences, especially to the victims and their families, and I offered our Japanese friends whatever assistance is needed," Obama said at a midday news conference.

"I'm heartbroken by this tragedy," Obama said.

"The Japanese people are such close friends of ours," he added. "That just makes our concerns that much more acute."

Obama said Kan told him that so far there were no signs of a radiation leak at a nuclear plant hit by the quake.

Earlier, US Secretary of State Hillary Clinton had said US Air Force "assets" in Japan had delivered coolant to a nuclear plant. However, a US official said Japan had asked the United States for the coolant, but ultimately handled the matter on its own.