A top aide of Prime Minister Menachem Begin bluntly advised a U.S. senator 10 days ago not to let worry over Arab oil affect U.S. peace plans for the Mideast, adding that Israel itself was in position to "handle" the oil question if the need ever arose.

That apparent reference by Gen. Ariel Sharon to a possible future Israeli operation against, say, Libya's oil fields did not go down well with Sen. Jacob K. Javits, a leading member of the pro-Israel bloc in Congress.

Sharon, hero of the 1973 Yom Kippur was, is Begin's minister of agriculture. More important, he is chairman of the government's ministerial settlements commission, giving him a key role in Begin's interventionist policy on new Jewish settlements on the West Bank, one of the hottest issues between Begin and Carter.

What Sharon said may not reflect in any way the thinking of the prime minister, but it rang a new alarm in Carter's ears just three days before Begin arrives for crucial talks here. Indeed, it jarred official nerves throughout the Carter administration, nerves that have become unusually sensitive in the war of words between Washington and Jerusalem.

Sharon also advised Javits, who has tried hard to use his good offices as go-between for Jimmy Carter with Begin's new hard-line government, to tell the President that the West Bank legally belongs to Israel and to stop pressuring Israel to give it up.

What Sharon told Javits may only be a side drama, political gamesmanship to prepare the way for Begin's visit and keep the Carter White House off balance.

In fact, Mideast experts now see some reason to hope that Begin, an acknowledged territorial expansionist, might actually give a little on the crucial West Bank question - if first there were a clear "understanding" by the United States that Israel holds title to all of Judea and Samaria (a title, Begin insists, that derives from the Old Testament delineation of the "Land of Israel").

But Carter is unlikely to try to bestow on Israel a territorial right over 600,000 Palestinian Arabs that is denied vehemently by all Arab countries and consistently by every U.S. President since Israel seized the West Bank in 1967.

Consequently, if Carter can't pay the prime minister's price for genuine (as opposed to pro forma ) Israeli bargaining with the Arabs on the West Bank, another way to avoid an immediate impasse in next week's talks must be found.

What some diplomats here think Begin has in mind is an appeal to the President for delay. In view of the disagreements between the United States and Israel and of the multiple and sometimes conflicting United Nations resolutions and other international documents dealing with the long Arab-Israeli struggle, the United States and Israel should sit down together and define precisely where each stands.

That would give Begin more time to consolidate his new government (a job he has performed with great skill so far) and to let his demands for territorial expansion at Arab and U.S. expense sink in, in both the United States and Israel.

The rapid coalescing around Begin, despite his radicalism, has been widely noted. A case in point is the decision of Abba Eban, a longtime Israeli dove held in high regard here, to tour the United States for Begin following Begin's talks with Carter. IN agreeing to go, Eban said he wanted to restore Israel's high standing in the United States as it was "when there was no talk about a Palestinian homeland and a return to the June 1967 borders" (a surprising statement in view of the Nixon policy denying that final borders should reflect the "weight of conquest" and calling for a return to 1967 borders with "insubstantial" changes).

Eban's decision is another mark of Begin's growing prestige both in Israel and among the American Jewish community. Moreover, Israel is in excellent military shape to risk prolonged delays in arriving at any consensus with Jimmy Carter - if a consensus is possible.

High defense officials in Tel Aviv told the respected Jerusalem Post two weeks ago that since the Yom Kippur war the Israeli air force has reached the size of the French and British air forces combined. Its armored strength on the ground, they said, is half that of the entire armored strength of the North Atlantic Treaty Organization (an understatement, in the view of some U.S. officials).

Moreover, Begin has a $3-billion U.S. military pipeline, the payoff for Israel's modest 1974 pullback from the Suez Canal and the Syrian plain. President Carter has pledged there will be no interuption of those weapons, guaranteeing Israel military superiority over the Arabs far into the future, unless Moscow starts a major rearming program.

So delay might suit Begin. Sharon's background noise may give the White House trouble sleeping, but the real action is in the center ring, where Begin's footwork looks faster everyday.