China Is Rebuilding a Country It Helped to Destroy in 13-Year War : Asia: Cambodia was ravaged by Khmer Rouge guerrillas, whom the Chinese armed. Now Chinese troops are part of the U.N. peacekeeping mission there.

Chinese soldiers are repairing roads and guarding the peace in Cambodia, which their country helped destroy by arming the Khmer Rouge guerrillas for nearly 13 years.

China’s participation in its first U.N. peacekeeping operation is part of an effort to regain international standing after the bloody military crackdown on its pro-democracy movement in 1989.

The U.N. Transitional Authority in Cambodia would not have been possible if China had not joined the other permanent Security Council members to draft the Cambodian peace accord signed in Paris in October, 1991.

“My job here is to make a new start, to implement the Paris agreement, to push the peace process forward,” said Sun Yuxi, the second-ranking Chinese diplomat in Phnom Penh.

Recently, China has been putting pressure on the Khmer Rouge to begin disarming and stop violating the Paris treaty.

In August, Deputy Foreign Minister Xu Dunxin met in Bangkok with Khmer Rouge leaders. An Asian diplomat, speaking on condition of anonymity, said Xu told them, in essence, “If you don’t listen to us, you will be isolated from the entire international community, including China.”

Beijing also has been improving relations with the government in Phnom Penh, which Vietnam installed after invading Cambodia in 1978 and driving the Khmer Rouge from power.

Following a visit to China by Chea Sim, leader of Cambodia’s ruling party, Chinese relations with the government are at least on the same level as those with the Khmer Rouge, the Asian diplomat said.

China supported the Khmer Rouge even though the radical Communist movement tried to eliminate Cambodia’s ethnic Chinese after gaining power in 1975. Estimates of the number of people who were killed or died of starvation under the Khmer Rouge range from several hundred thousand to more than 1 million.

U.S. intelligence agencies say China gave the Khmer Rouge military aid of about $100 million a year in an effort to contain Vietnam, a Soviet-sponsored adversary with which it fought a brief border war in the 1970s.

Now the Soviet Union is gone, Vietnam is preoccupied with economic problems and China is concentrating on its own economy.

Diplomats say China stopped supplying the Khmer Rouge months before the Paris treaty. At an international aid conference in Tokyo in June, the Chinese pledged $10 million for Cambodia’s reconstruction, to be shared by all factions.

China is the only Communist nation with personnel in the U.N. Cambodian operation. The main group is a 399-member army engineer corps repairing the military airfield in Phnom Penh and two main highways, Routes 4 and 6, including bridges. Much of the damage was done by Chinese-supplied shells and mines.

Forty-five other Chinese serve with the U.N. military observer group that investigates truce violations and tries to smooth disarmament of the Cambodian factions.

They include Maj. Li Zhijun, a battalion commander from Beijing who said he was happy both to serve an international mission and practice his English.

Li is careful to be a neutral U.N. officer, but he knows his country’s ties with the Khmer Rouge can open doors.

He recently made a dangerous drive into a mined Khmer Rouge stronghold in southern Kampot province to try to persuade the guerrillas to disarm. He told a man who might be in touch with the Khmer Rouge: “Tell them I am from China and I want to speak with them.”

Another Chinese observer, Capt. Li Qiuming from Zheng Zhou, is involved in trying to control fighting between Khmer Rouge and government forces in Kompong Thom, a central province.

“We’re here for the peace of Cambodia,” he said.

The Chinese engineers get along well with the large ethnic Chinese community, but most cannot speak foreign languages and keep to themselves.

A satellite antenna brings Chinese television to the dormitory.

Many other U.N. soldiers have Cambodian cooks, but the Chinese prepare their own meals at the Pochentong airport work site, where a young soldier recently was seen sitting on a stool, peeling Chinese green squash.

“Chinese people prefer Chinese food,” said Maj. Lu Xin Cai of Jiangsu, near Shanghai.