A senior U.S. Defense Department official today informed Egyptian leaders that President Carter had agreed in principle to supply Egypt with the advanced F15 "Eagle" jet fighter, but cautioned them to expect a four-year delay before the first deliveries, U.S. sources said.

After conferring with Vice President Hosni Murbarak, U.S. Assistant Secretary of Defense David McGiffert insisted that the U.S. military supplies to Egypt, which will also include F16 fighters and M60 tanks, will not alter the balance of power in the Middle East.

His remarks appeared to come in response to Israeli complaints about the U.S. arms package for Egypt, especially about the F15 -- considered the most sophisticated fighter in the U.S. arsenal.

U.S. sources here disclosed that the Carter administration plans to add $200 million to an aid request to help Egypt finance the American weapons.

The Egyptian Defense Minister, Gen. Kamal Hassan Ali, has hailed the Carter administration's willingness to supply the F15 as a step putting Egypt and Israel "for the first time on equal footing" in access to sophisticated American arms. The F15, which Israel already has, is regarded here as an important symbol on how President Anwar Sadat's peace policies can pay off in friendship with Washington.

McGiffert is in Cairo to relay President Carter's response to a long Egyptian shopping list for U.S. arms.

McGiffert and his team of negotiators orginally tried to dissuade the Egyptian from insisting on the $17 million Eagle, the U.S. sources said, arguing that it is too complicated and expensive for Cario's needs.

But Sadat and Ali apparently held firm, underlining the plane's value as proof to their Arab foes that the United States is willing to provide its friends with the most advanced military equipment despite Israeli objections. Another factor in the argument, the sources added, was the F15's, which the United States already has agreed to supply.

McGiffert is said to be emphasizing to the Egyptians that Carter's willingness in principle to supply the F15 still depends on approval in Congress of a broad military refitting program being prepared for Egypt.

The aid package, estimated to be worth about $4 billion over five years, also includes Improved Hawk antiaircraft missiles, M113 armored personnel carriers and F4 Phantom jets. In addition, preliminary talks are under way for assembly in Egyptian factories of the Bell 214-ST helicopter and the F5 jet fighter.

The delivery delay for the F15s is in part the result of a backlog of orders for the fighters, which are manufactured by McDonnell Douglas. In addition the U.S. Air Force, the air forces of Israel, Saudi Arabia and Japan have the F15 on order.

The delay also softens the political impact in Congress, analysts pointed out. Egypt can assert it has agreement in principle to get the planes, while the Carter administration can tell Israel's congressional supporters that Israel is receiving them far in advance ofEgypt.

The first F16s are expected to be delivered here before the end of 1980, U.S. sources said.To help finance their purchase along with the M60 tanks, they added, the Carter administration plans to add about $200 million to a $350 million addition in arms aid requested for the 1981 fiscal year beginning Oct. 1. This would bring the total request before Congress to more than $1 billion.

The large amount of aid involved, coupled with the decision to provide the most advanced U.S. warplanes, demonstrate the degree to which Washington appears willing to get involved in a close strategic and military relationship with Sadat.