WASHINGTON -- The U.S. pledged to help Chile after a powerful earthquake struck Saturday and kept watch on a tsunami heading for Hawaii.

The U.S. Embassy in Chile was working to learn the whereabouts of U.S. citizens in Chile, both diplomatic employees and other Americans who may have been living there or visiting, State Department spokeswoman Megan Mattson said.

There were no reports of U.S. casualties, and the U.S. military said it had no reports that any of its forces had been affected either on land or at sea.

"We are closely monitoring the situation, including the potential for a tsunami," White House Press Secretary Robert Gibbs said. "Our thoughts and prayers are with the people of Chile, and we stand ready to help in this hour of need."

The Pacific Tsunami Warning Center issued a tsunami warning - its highest alert - for Hawaii. The first waves were expected to arrive in Hawaii at 4:19 p.m. EST. A lower-grade tsunami advisory was in effect for the coast of California and an Alaskan coastal area.

Mattson said the U.S. had reached out to the Chilean government. In cases of natural disasters, the affected country usually accepts an offer of help made by the State Department, which then could ask the Defense Department to help with any relief mission. The U.S. Southern Command, which overseas the U.S. military presence in South and Central America had not yet received any request, Sgt. Santita Mitchell of the command's public affairs office in Miami said.

The State Department advises Americans seeking information on family and friends in Chile to contact the Bureau of Consular Affairs at 1-888-407-4747.

There are 118 embassy employees and am estimated 1,000 other Americans living in Concepcion and the surrounding area. The number of U.S. citizens throughout the South American nation was not available.

Original AP story below:

SANTIAGO, Chile -- Chile's government says 76 people are confirmed dead in a giant earthquake that has collapsed buildings and set off a tsunami.

The death toll comes from the deputy interior minister, Patricio Rosende. His boss, Edmundo Perez Yoma says: "the death toll will continue rising."

The magnitude-8.8 earthquake has caused a huge wave that reached a populated area in the Robinson Crusoe Islands off the Chilean coast. Tsunami warnings have been issued over a wide area, including South America, Hawaii, Australia and New Zealand, Japan, the Philippines, Russia and many Pacific islands.

The earthquake struck early Saturday.