A high-level Chinese delegation flew to Phnom Penh yesterday for talks that appeared aimed at halting the bitter border fighting between Vietnam and Cambodia.

Madame Teng Ying-chao, widow of the Chinese Premier Chou En-lai and a vice chairman of the National People's Congress, was accompanied on the mission to Cambodia by three top members of China's Foreign Ministry.

Speculation that China may be trying to mediate the border war between the two Indochinese Communist neighbors was fueled by the presence in Peking of Vietnamese Vice Foreign Minister Phan Hien, who is considered his country's leading expert on border questions. Hien arrived in Peking on Jan. 9.

Hanoi Radio, meanwhile, charged yesterday that Cambodia has continued to stage daily raids into Vietnamese territory.

Vietnam said Cambodia massed "a large force consisting of many battalions" in the area adjoining Long An-Province on Tuesday, and that elements of this force penetrated more than a mile and a half into Vietnam.

As of late Tuesday, the "Cambodian forces still occupied a number of areas in Vietnamese territory," Hanoi charged.

Cambodian Premier Pol Pot, however, renewed his country's claim that it was Vietnam that had invaded Cambodian territory, and contended that "the aggressor Vietnamese forces" had been "trounced and driven back to the border."

In a speech broadcast by Phnom Penh Radio Tuesday, Pol Pot claimed that Cambodian forces had killed or wounded "more than 26,000 Vietnamese troops - decimating five divisions of the regular Vietnamese Army."

Western intelligence analysts consider the claims of both sides to be inflated, and say Vietnamese troops still appear to be entrenched in the Parrot's Beak and fishhook areas of Cambodia.

Pol Pot, however, made no reference in Tuesday's speech to the possibility of peace negotiations.

"If the Vietnamese side ends it interference, subversion, strafing, shelling, aggression and annexationist acts against Democratic Cambodia, and renounces its" efforts to take Cambodia as a satellite in an Indochina federation, Pol Pot said, "there will be no reason for use to quarrel with each other."

Nevertheless, Vietnam yesterday reiterated its willingness to seek a settlement to the border war through negotiations, and warned that its patience was wearing thin.

"The more Vietnam displays its patience and self-restraint and the more it expresses its desire to quickly hold negotiations to solve the border issue, the bolder Cambodia becomes," Hanoi Radio said.

"If (the Cambodian authorities) continue their criminal acts and stubbornly reject negotiations, they will have to bear full responsibility for all the consequences arising from their acts," Vietnam said.

The Carter administration, meanwhile, condemned Phnom Penh yesterday for what it called one of "the most flagrant and massive abuses of human rights to be found in the world - that in Cambodia."

Deputy Secretary of State Warren Christopher, in a speech to the National Media Conference, said that "hundreds of thousands of human beings - not only supporters of the former regime, but people from all elements of society - have perished" since the Communists took over in April 1975.

Christopher's statement represented an upward revision of the U.S. estimate of the minimum death toll in Cambodia. Assistant Secretary of State Richard C. Holbrooke told a House subcommittee last July "the number of deaths appear to be in the tens if not hundreds of thousands."

U.S. officials said yesterday there was no way of giving any accurate estimate of the death toll - which some journalists and scholars have guessed to be as high as 1.2 million. But they said the United States now believes the number of dead certainly exceeds 100,000.