The wide-ranging list includes Russia and Central American countries like Guatemala, El Salvador and Costa Rica and the U.S. state of Hawaii. The weather service's bulletin said it was intended "as advice to government agencies.
The quake, which struck near the coast of Honshu, Japan, on Friday afternoon, unleashed a wall of water that rushed in toward land, leveling houses and bashing cars in its path and apparently killing hundreds.
Some officials feared that the fast-moving waves from a tsunami could be so high that they would wash over entire islands in the Pacific, a spokesman for the International Federation of Red Cross and Red Crescent Societies said Friday.
There was some good news on the island of Guam, where the tsunami warning was lifted. Police reported no damage or injuries. Indonesia also lifted its warning.
In the country's northeast city of Manado, residents rushed to higher ground as emergency officials corralled those who remained in low-lying areas.
"Experts are saying that it could be anywhere from 4 to 10 meters. That's higher than some of the Pacific islands are above sea level. We just have to do the calculations to see that this is a real threat," federation spokesman Paul Conneally said.
"In a situation like this, we have to prepare for the worst-case scenario," he added.
But Gerard Fryer of the Pacific Tsunami Warning Center said even though waves could cause significant flooding, "washing over islands is not going to happen."
Tsunami waves can travel at speeds of 800 kilometers per hour.
"The tsunami is more than one wave, and the waves can be separated by 20 minutes or half an hour. So just because you see a wave come up and then go back in the ocean again, that doesn't mean it's over," Fryer said.
Sirens sounded in Hawaii around 10 p.m. Thursday (3 a.m. ET), warning residents they could expect tsunami waves five hours later. The Pacific Tsunami Warning Center said Kauai was the first Hawaiian island hit by the waves, which swept across the remainder of the island chain as 6-foot surges pushed waves ashore.
Officials said such ocean surges can push water as far as a quarter of a mile inland.
The West Coast and Alaska Tsunami Warning Center early Friday issued a tsunami warning for coastal areas along the U.S. and Canadian west coasts. The tsunami warning includes coastal areas of California and Oregon from Point Conception to the Oregon-Washington border. It also includes coastal areas of Alaska from Amchitka Pass to Attu.
The Northern California counties of Del Norte and Humboldt issued evacuation orders Thursday, according to California Emergency Management spokesman Brad Alexander.
San Mateo County also issued evacuation orders, as well as areas in Southern California stretching from Santa Barbara to the Mexican border.
Wendy Watson-Wright of the United Nations Educational, Scientific and Cultural Organization warned nations to be on alert.
"This is a massive one, and it will have different effects depending on the location, on the seabed and on other sorts of characteristics," she said. "But clearly, this is very, very large, and from that perspective, all countries need to be alert, on standby for the moment."
In the Philippines, the government has evacuated 20 coast areas. Officials said they were getting reports from Isabela province of "unusual waves" hitting the coastline. Benito Ramos, the country's disaster management director, said waves have hit the coastal areas of Aparri, Cagayan and Basco, Batanes.
Ramos said the tsunami alert remained elevated to a level two across the country as a precaution.
The administrator of the U.S. Federal Emergency Management Agency said employees are ready to assist state and local officials.
"We remind everyone who lives in the region to monitor their local news for instructions from their state and local officials and if told to evacuate -- evacuate," Administrator Craig Fugate said.
Russia's Emergency Situations Ministry said more than 11,000 people living in dangerous areas had been evacuated after a tsunami warning was issued for the Kuril Islands. Ships docked in open ports were heading back out to sea to avoid being hit by tsunami waves, the ministry said.
Chip McCreary of the Pacific Tsunami Warning Center said officials estimated the quake was already causing waves of up to 2 meters above normal sea level.
"This is a very large earthquake. We've evaluated it as about the same size as the earthquake last year in Chile. However, it's much closer to the Hawaiian islands than the Chile earthquake.
Waves are expected to begin hitting both Australia's and Chile's coastlines at around noon ET. The National Weather Service list includes Japan, Russia, the Philippines, Indonesia, Papua New Guinea, Australia, Fiji, Mexico, New Zealand, Guatemala, El Salvador, Costa Rica, Nicaragua, Panama, Honduras, Chile, Ecuador, Colombia, Peru and the United States.
Numerous Pacific islands, including some U.S. territories, are also on the list. Friday's 8.9-magnitude temblor in Japan was the largest earthquake since a 9.0-magnitude earthquake struck the Banda Aceh area of Indonesia on December 26, 2004, causing a massive tsunami that killed about 250,000 people in 14 countries and washed away entire communities. The tsunami caused nearly $10 billion in damage and more casualties than any other tsunami in history, according to the United Nations.
The earthquake, initially reported as a 7.8 earthquake, was upgraded to an 8.9 quake.
When you jump a magnitude from 7 to 8.9, it's not 10 times stronger, it's 1,000 times stronger," CNN International meteorologist Ivan Cabrera said. "With an ... earthquake that shallow, that close to shore, there will be more than one tsunami.