The Reagan administration is expected to decide shortly to send a small number of Stinger antiaircraft missiles to Chad to help offset new weapons and manpower that Libya is obtaining from Iran and Lebanon in preparation for the next round of fighting in northern Chad.

An administration source familiar with interagency deliberations on the Stinger question predicted that the White House will decide "in the next couple of weeks" to send up to two dozen of the high-technology weapons to establish a credible deterrent against Libyan bombing of Chad's northern positions and that the first missiles will arrive there "within 30 to 90 days."

France, Chad's main arms supplier, has been told of the pending U.S. decision and has not objected, the source said.

The decision to send Stingers, sought by Chadian President Hissene Habre, apparently reflects administration desire to show strong support for Chad's struggle to oust Libyan troops from the disputed 60-mile-wide Aozou Strip in northern Chad.

The source said that while there were conflicting views within U.S. intelligence and military circles over whether Chad needs Stingers, there was a strong desire to send them if only as a show of political support.

The source said the administration has consulted the Senate and House intelligence committees and found little opposition provided steps are taken to assure that the sophisticated weapons do not fall into Libyan hands.

Saying no Stingers have yet been sent, U.S. officials denied Libya's recent claims to have captured some of the missiles from the Chadian army. They said Libya instead may have captured U.S. Redeye antiaircraft missiles sent earlier to Chad.

The source said the administration has been influenced by evidence that Libyan leader Moammar Gadhafi has obtained chemical warfare weapons from Iran and reports that he is recruiting more than 1,200 battle-hardened militiamen from Druze and pro-Syrian factions in Lebanon.

The United States has included 2,000 gas masks in an emergency $32 million military aid program for Chad this year.

Chad and Libya last Saturday agreed to a cease-fire arranged by Zambian President Kenneth Kaunda, chairman of the Organization of African Unity. But U.S. analysts believe Gadhafi has agreed to only a temporary halt in hostilities to regroup forces after Chad routed Libyan troops at Maatan and Sarrah Sept. 5-6 in southern Libya.

Chad claimed it killed 1,700 Libyans, captured more than 300 others and destroyed 26 or 28 Soviet-made aircraft. The United States estimates that 1,500 Libyans died, but believes that the claims of planes destroyed were exaggerated, the source said.

Yesterday, news reports from Lebanon said Libya is recruiting Druze and other pro-Syrian militiamen to strengthen its shattered army, which has suffered 4,000 deaths, 1,000 wounded and 1,300 captured during a string of defeats at the hands of Chadian forces.

Most of the Lebanese recruits are from Walid Jumbatt's Druze Progressive Socialist Party, which has gotten financial aid, arms, gasoline and other assistance from Gadhafi for several years.

The reports said Libya is offering $500 a month for a mercenary private, $1,000 for an officer, extra allowances for mercenaries who have children, a six-month advance payment and $20,000 for the family of any killed in action.

U.S. officials believe the biggest battle of the Chad-Libya war has yet to be fought and will involve a Chadian attempt to recapture the Libyan-held town of Aozou inside the Aozou Strip. Chad took the town in early August, but lost it later that month.