An Israeli Army officer today publicly contradicted Prime Minister Menachem Begin, testifying that Begin had asked the Army about events at a West Beirut refugee camp hospital hours before Begin has acknowledged knowing anything about the massacre of Palestinian civilians.

A second witness who appeared before the Israeli judicial board of inquiry that is investigating the massacre in two West Beirut refugee camps testified that U.S. envoy Morris Draper asked Israel to remove the Lebanese Christian militia units from the camps about 12 hours before the militiamen actually left.

Draper's message was relayed to David Kimche, director-general of the Israeli Foreign Ministry, and to the Defense Ministry in Tel Aviv, according to the witness, Ariel Kenet. But Kenet, a Foreign Ministry employe, said that he does not know whether anything was done about the request.

The Army officer who testified today, Lt. Col. Zev Zecharin, is the senior aide to Israeli Army Chief of Staff Lt. Gen. Rafael Eitan.

Begin has maintained throughout the investigation that he first learned of the massacre from a news report at 5 p.m. Sept. 18, hours after the militia units had left.

This was first called into question by Defense Minister Ariel Sharon, who testified last month that Eitan told him of a telephone conversation with Begin the morning of Sept. 18 in which Begin asked about unspecified events at Gaza hospital, which is in the Sabra refugee camp.

When Begin testified last week, he flatly denied Sharon's assertion. Begin said it was impossible for him to have talked to Eitan that morning because he was in his synagogue from about 8:30 a.m. to 1:30 p.m.

Zecharin, however, testified today that at 10:30 a.m. Sept. 18 Eitan told him he "had spoken with the prime minister and the prime minister had asked to receive data on what happened in Gaza hospital."

It has never been clear in any of the public testimony precisely what Begin is said to have asked to know about the hospital or on what he based his inquiry.

Kenet's testimony today was the first concrete evidence of what has been vaguely referred to during the investigation as "American pressure" to remove the militia from the camps.

Kenet told the inquiry board that he was the Foreign Ministry's duty officer on Sept. 17, and that at 6 p.m. that night he received a message from Bruce Kashdan, the Foreign Ministry's representative in Beirut.

According to Kenet, the message said that "Morris Draper says that he has received reports, or that he has learned, that [Phalangist] personnel were seen in the Shatila camp, and that their presence in the camp could or may lead to undesirable developments. He asked Bruce Kashdan to convey to those concerned that Israel, which has made a commitment previously to safeguard the welfare of the civilians and law and order, should intervene or take steps in order to prevent something which he believes may develop."

There is no indication that Draper's message had any impact.

In his testimony, Zecharin also disputed a portion of Sharon's public testimony. Zecharin said that on Sept. 14, before it was certain that Lebanese president-elect Bashir Gemayel had been assassinated, Sharon and Eitan discussed sending the Phalangist militia units into the camps.

Reminded by Judge Aharon Barak, a member of the commission, that Sharon had testified the Phalangist militiamen were not discussed at this meeting, Zecharin replied, "I am 100 percent certain that the Phalangists were discussed."