Questions raised in the US Congress about Israeli tactics in Lebanon are not likely to lead to any restrictions on American aid to the Israelis, say key senators and congressmen.
But congressional staff aides indicate that Israel's Prime Minister Menachem Begin did not win any friends in the Congress - and probably lost a few - during his just-ended visit here. It is clear that Israel can no longer count on the almost automatic support that it had from some senators and congressmen for almost any action it took.
What has most offended many of these lawmakers are reports from Lebanon of extensive civilian casualties resulting from Israeli bombing and shelling. After participating in a meeting with Prime Minister Begin here on June 21, House Foreign Affairs Committee Chairman Clement J. Zablocki (D) of Wisconsin said he thought that Israel had violated the requirement that US-supplied weapons be used only for defensive purposes. Representative Zablocki plans to raise qustions about this when Reagan administration officials are called to testify before his committee next month.
If they wanted to, the two houses of Congress could pass a joint resolution determining that American weapons were not used for defensive purposes in Lebanon, thus requiring a cut in aid to Israel. But congressional staff specialists say this is not likely to happen.
Instead, senators and congressmen are likely to press the administration to make its own determination on that subject. President Reagan apparently did not raise the subject, however, in his meeting with Begin June 21.
In a meeting with senators June 22, Begin was questioned about press reports alleging that Israel had used ''anti-personnel'' cluster bombs in the Lebanon fighting. Begin was reported to have said he did not know if such weapons were used. State Department officials said that Israel had not yet replied to queries from the US government on that subject.
According to Senate sources, most senators left the meeting with Begin feeling more critical, rather than less critical, of the Israeli invasion.
''I doubt that anyone walked out more sympathetic with Israel,'' said one source.
First of all, Begin opened the discussion with a more than 30-minute monologue, which offended some senators. Then he replied to questions about Israeli actions in a fashion described as ''unyielding.'' Finally he appeared to imply that the US was doing itself a favor by giving aid to Israel because it was in the American interest.
In all, about half a dozen senators out of more than 30 present confronted the Israeli leader with harsh questioning. Only one, Sen. S. I. Hayakawa (R) of California voiced unambiguous support for the Israeli action in Lebanon.
After the meeting was over Sen. Charles Percy (R) of Illinois asserted that none of this meant that there had been erosion in congressional support for the security of Israel. It appeared, however, that there had been erosion in the support that once existed for Begin.
The Israelis, for their part, seem to think that the change in the mood on Capitol Hill is largely due to press reports that they say exaggerate the extent of civilian casualties in Lebanon. The Israelis dispute Palestinian assertions that more than 10,000 have been killed, and a report from a Red Cross official that the number of people killed in the town of Sidon alone had reached as high as 1,500.
But on Capitol Hill there is tendency to believe that while some casualty figures may have been exaggerated, the number of civilians killed does run into the thousands and that the number of those affected in some way by the fighting into the hundreds of thousands.
There is also a growing concern that despite their protestations to the contrary, the Israelis may find a pretext to launch an attack into crowded west Beirut, thus causing additional heavy casualties.