Soviet and Afghan troops have extended their drive against rebels in eastern Afghanistan to a second province, Western diplomats and insurgent leaders said yesterday in Pakistan.

Rebel representatives in Preshawar, Pakistan, said Afghan troops backed by Soviet soldiers, tanks and fighter aircraft were battling the guerrillas in Paktia Province. A week ago, the combined forces began a drive in Kunar, the neighboring province along the Pakistani border.

Western diplomats in Islamabad, the Pakistani capital, said they had confirmed reports of "serious encounteres" in and around the Paktia town of Chigasarai.

"The fighting in Paktia is obviously an overflow from the heavy battles that began in Kunar Province last week and which are still continuing," a Western military analyst said.

Rebels have claimed to control most of Paktia Province, with the exception of a few main cities.

In Islamabad, Pakistani President Mohammed Zia ul-Haq told reporters he turned down a U.S. military and economics aid off because it would have jeopardized his country's nonaligned status, not because it was too little.

The $400 million in U.S. aid was offered to strength Pakistan after Soviet troops invaded Afghanistan in December.

Zia originally called the aid proposal "peanuts." But yesterday he noted the nonaligned status of nearly all other Moslem countries and added that in rejecting the aid, Pakistan "is maintaining its posture toward Islamic unity."

Addressing an engineers' convention, Zia also declared his determination to conitnue Pakistan's nuclear development "for peaceful purposes . . . . which is extremely vital for the economy of the country."

Zia noted the scarcity of conventional sources of energy, saying Pakistan produces 13 percent of its oil needs.

In an interview Sunday, Zia stressed nonalignment and pledged "to buy total security" in the wake of the Soviet intervention next door. "We have talked with the Soviet Union" and "will be talking with the United States," he hold the West German news magazine Der Spiegel.

In Moscow, the Soviet Communist Party daily Pravda charged that American agents were continuing subversive acts in Afghanistan and "this makes remote the possibility of a withdrawal of Soviet troops."