Secretary of State Alexander M. Haig Jr. conferred with Egyptian President Hosni Mubarak today, reportedly pledging to direct personally an "active U.S. role" in reviving the stalled Egyptian-Israeli negotiations over Palestinian autonomy.

Foreign Minister Kamal Hassan Ali, who also attended the 90-minute meeting, reported Haig's pledge. Ali said Mubarak promised full Egyptian cooperation and characterized Haig's pledge as "very essential to push forward progress" in the negotiations.

Haig's talks kicked off an exploratory mission in which he is seeking to gauge the differences between the Egyptian and Israeli positions before recommending to President Reagan a strategy for achieving a successful autonomy agreement. The talks have dragged on for 20 months.

Despite this upbeat rhetoric, sources on both sides stressed that Haig's efforts are just beginning and that the secretary, while serious about assuming some sort of personal role in prodding the talks to completion, still has not formulated any clear approach.

There had been talk in Washington that the Reagan administration hoped to push through an accord before the end of April, when Israel is scheduled to return the occupied Sinai peninsula to Egypt. The administration fears that after that time both Israel and Egypt will lose their incentive to pursue the autonomy talks seriously and the broader peace process will lose momentum.

However, Haig, even before his arrival here, has been stressing that the United States is not linking the autonomy talks to Israel's withdrawal from the Sinai and has no timetable or deadline for achieving an accord. The same point was made today by Ali, and Egyptian officials said privately that an agreement by April would be almost impossible.

At issue is the commitment made by Israel and Egypt, under the Camp David accords, to work out a system of interim self-rule for the Palestinian inhabitants of the West Bank and Gaza Strip, territories captured by Israel in 1967 and controlled by it ever since.

After a 13-month break in the negotiations, the two governments resumed talks last September with the idea of achieving not a fully detailed agreement but a declaration of principles covering the main points of what the autonomy system is to include.

The idea is that this would be sufficiently detailed to permit putting the self-rule system into effect, while further details are worked out with Palestinian participation at a later time.

However, even with that stripped-down approach, a wide gap remains between Egypt's call for "full autonomy for the Palestinians" and the desire of Israeli Prime Minister Menachem Begin's government to retain a significant degree of control over the occupied territories.

The Reagan administration has been criticized for not doing more to help bridge the gap, and it was partially in response to this criticism that Haig, who had focused most of his earlier Middle East policy planning on strategic questions, undertook his present mission.

There has been considerable speculation that his talks with Mubarak and on Thursday with Begin will result in appointment of a speical U.S. negotiator.

That tactic was used in the early stages of the autonomy negotiations by then president Carter, but Reagan has left the position unfilled since he took office. The Israelis are anxious for the United States to inject a special negotiator into the talks, and the Egyptians, while cooler to the idea, are understood to have informed Haig that they will not object.

Haig also is known to have doubts about appointing a special negotiator. The secretary apparently questions whether he would have clear-cut authority over whoever is named to the job. Haig's hesitancy has caused additional speculation about the possibility of him letting the Egyptians and Israelis make a try at accelerated negotiations and then returning to the Middle East later this year to undertake a shuttle mission aimed at wrapping up the accord.

Today, though, both Haig and Ali sought to play down the idea of shuttle diplomacy. When reporters asked if that was the meaning of the talk about Haig's "personal involvement," the foreign minister replied: "We are not talking about it as shuttle diplomacy. There are other means."

Egyptian sources said Haig was concentrating on getting a minutely detailed picture of the Egyptian position and had given no sign of what course he is likely to follow. U.S. officials accompanying the secretary responded to questions about how he will proceed by saying, "We'll have a better idea after the trip is over and we get back to Washington to assess what we've heard out here."

The main disagreement with which Haig will have to contend involves the powers to be given the self-governing authority that is to run the occupied territories under the autonomy system. Egypt wants to give it broad legislative, executive and judicial powers, but Israel, fearing it could provide the nucleus for an independent Palestinian state, wants to limit the self-governing authority's powers largely to municipal functions.