Several countries not originally interested in a Pacific-wide tsunami drill have been signing up for the exercise after flaws occurred in warnings about a recent earthquake near Tonga.

Since the 7.9-magnitude temblor hit May 3, the Pacific Tsunami Warning Center in Hawai'i has experienced a spike in replies to invitations about the test that were sent out by a U.N. agency two months ago.

"It's convinced people that they really should participate," said Gerard Fryer, acting director of the center in 'Ewa Beach that will launch mock bulletins of two simulated earthquakes beginning Tuesday.

A Pacific warning system has been in place since 1965, but a full ocean-wide exercise has never taken place, according to the Paris-based U.N. Educational, Scientific and Cultural Organization. The mock earthquakes — one off the Chilean coast and another near Luzon in the Philippines — would be strong enough to generate the deadly waves.

The mock event will also be monitored by tsunami centers in Alaska and Japan.

In addition to a list of 28 countries from Australia to Nicaragua selected to take part in the test, researchers have also gotten calls from other Pacific Rim countries asking to join.

"It looks like most of the member countries throughout the Pacific are going to be involved," Fryer said. "And a couple of countries that are not formally part (of the program) will also be participating in the event."

Among those will be Tonga, which was inadvertently left off a list of areas predicted to be hit by a possible tsunami from the May 3 earthquake. The communication failure raised troubling questions about the effectiveness of such alerts, which have come under global scrutiny since an earthquake-driven tsunami in the Indian Ocean nearly 18 months ago left at least 216,000 people dead or missing.

Fryer said countries will find out whether their emergency systems can get the warnings in time to prepare.

"The really important thing about this is that it is forcing us to verify all the communication links," he said.

Tonga's national disaster office deputy director, Mali'u Takai, said there would be "a whole countrywide test" of the islands' emergency controls as well as checks on "the biggest issue we're facing now — communications problems."

He said a power failure after the recent earthquake prevented warnings from getting through to Tonga — an isolated, 170-island archipelago about halfway between Australia and Tahiti. The office would be working on how to disseminate information once it is received, Takai said.

Takai noted that even if warnings had reached Tonga, people would have had only 15 minutes before a wave would have hit the islands.

"The islands are so tiny, some of them are quite flat," he said. "Depending on the warning time (available), we may not have the chance to evacuate ... and will have to do the best we can in the circumstances."

Countries included in the drill are not required to carry out a test on land. It's unclear which nations will use the scenario to alert local emergency responders.

In Hawai'i, state Civil Defense officials will have a minimal participation — limited to workers at computers answering a few phone calls — because of an annual hurricane drill happening in the same week, said spokesman Ray Lovell.

"We will try to deal with both of them," he said. "The benefit that we will get out of it is being able to deal with two scenarios at the same time ... it could happen."

Scientists will speed up the two simulations to cut the first drill to about eight hours, Fryer said, and the second test should last about five hours. Costs should be limited to a few overtime hours.

The entire exercise would be canceled if a real earthquake of magnitude 7.0 or higher were to occur anywhere in the Pacific during the drill. UNESCO expects to complete a report with feedback from participating countries by late June.