COLOMBO, Sri Lanka (AP) _ The Tamil Tigers separatist guerrillas have appointed a Sri Lankan-born British Tamil to start peace talks with the Sinhalese-dominated government, officials and Tamil sources said today.

Anton Balasingham, recently named head of the political section of the Liberation Tigers of Tamil Eeelam, was expected to arrive here from London ''in the next couple of days,'' sources close to the rebels said.

The sources spoke on condition of anonymity.

In a surprise move during the weekend, the Tigers declared they were ready to begin peace talks with President Ranasinghe Premadasa.

The declaration came after the Tigers were blamed for three days of bombings that killed at least 79 people.

So far there has been no explanation for the sudden change of heart by the largest Tamil guerrilla group.

The Tamil sources said Balasingham's first mission is to talk with the government about a time and place for the talks. After that, he will be a member of the Tigers' negotiating team, the sources added.

Evans Cooray, Premadasa's press secretary, said the president's office was notified shortly before midnight Monday that Balasingham had been designated to make arrangements for the talks. Cooray said the message was contained in a telex from the Tigers' information office in London.

Premadasa, who took office in January, had offered to start talks with both the Tigers and Sinhalese militants about ending the ethnic violence that has claimed more than 12,600 lives in this once-idyllic Indian Ocean island since 1983.

The Sinhalese extremists, whose group is called the People's Liberation Front, have not responded to the Sinhalese president's call.

Sinhalese have dominated Sri Lanka's government and military since the island, formerly called Ceylon, became independent from Britain in 1948. Mostly Buddhists, they make up 75 percent of the country's 16 million people.

Tamils, who are mostly Hindus, comprise 18 percent and say they are discriminated against in jobs and education.

Efforts by Premadasa's predecessor, President Junius R. Jayewardene, to make peace with the Tamil separatists spurred a violent backlash by ultranationalist Sinhalese who said the government was offering too many concessions to the Tamils.