Secretary of State Cyrus Vance arrived here tonight and immediately began talks with President Anwar Sadat over ways to break the deadlock blocking a peace treaty between Egypt and Israel.

Following the 1 1/2-hour private meeting, the beginning of a Vance shuttle between the two countries, a spokesman for Vance characterized the talks with Sadat as "very good, full and constructive."

U.S. sources cautioned, however, that it will take at least a few days to get a clear idea of whether Vance can mediate successfully the Egyptian-Israeli differences in time to meet the Dec. 17 deadline specified at the Camp David summit for negotiating the peace treaty.

Complicating the situation will be the funeral in Jerusalem Tuesday of former Israeli prime minister Golda Meir. Vance has been designated by President Carter as a member of the U.S. delegation attending the funeral.

As a result, U.S. officials said tonight, he will meet with Sadat again Monday evening and then fly immediately to Israel. While he is in Israel for the funeral, the officials said, Vance, out of respect for the occasion, will conduct no business related to the peace talks.

Instead, he will return to Cairo on Tuesday immediately after the services, resume his talks with Egyptian officials and then go back to Israel on Wednesday. After that, one official in Vance's party said, "We'll be playing it by ear."

Vance was sent to the Middle East by Carter to try to resolve two major problems that have snarled the U.S.-mediated peace talks for a month. Underlying his mission is increasing concern in Washington that a failure to reach agreement by the Dec. 17 deadline will erode support for the treaty in both countries and set a bad precedent for efforts to broaden the Camp David accords into a comprehensive Middle East settlement.

One issue involves Sadat's insistence that the treaty be accompanied by a letter setting out a timetable for beginning and completing separate negotiations on establishing Palestinian autonomy in the Israeli-occupied West Bank and Gaza Strip. Israeli Prime Minister Menachem Begin's government has refused to agree to such a timetable.

The other main sticking point concerns Egypt's desire to change an article in the draft treaty text stating that the pact will take precedence over the other treaty obligations of the two nations.

That would appear to preclude Egypt from assisting other Arab states that might come into conflict with Israel, and Sadat, fearful of charges that he is forsaking larger Arab interests to make a separate peace with Israel, regards acceptance of that article as too big a political risk.

Egypt also wants to change another article in the treaty text to allow the agreement to be reopened for possible revision at some future date. However, U.S. sources say they do not regard that issue as a serious problem and add that they believe it can be addressed by a clarifying letter accompanying the treaty.

In seeking to resolve the West Bank and Gaza problem, reliable sources say, Vance hopes to persuade the Israelis to accept a timetable on the understanding, spelled out in the treaty package, that it represents target dates rather than fixed deadlines.

The sources also say Vance hopes to persuade Sadat that he should accept the existing language in the draft treaty, possibly with an accompanying clarifying statement about Egypt's legal right to honor commitments to its Arab allies.

The possibliity that he might not succeed already has raised considerable speculation that another summit involving Begin, Sadat and Carter might be required. U.S. sources, while making it clear that Washington does not like the idea, still say that the need to reach a peace agreement is so compelling that "anything is possible in the last resort."