Former president Jimmy Carter arrived today for the start of a six-day visit that is being watched closely because of his public disagreement with Israeli policy.

At the outset of the visit by Carter and his wife, the former president and Prime Minister Menachem Begin met for almost an hour early tonight in an outwardly friendly manner. Smiling broadly for cameramen, the two men greeted each other warmly outside Begin's office in the Israeli parliament.

According to Uri Porat, Begin's spokesman, the men discussed the troop withdrawal negotiations in Lebanon, in which Begin expressed optimism that there would soon be an agreement, during a 20-minute portion of the meeting attended by aides. Carter and Begin then met for 30 minutes in private.

The public display of congeniality between the two men, however, masked deep disagreements between them that go back to what is generally regarded as Carter's greatest foreign policy accomplishment as president--the 1978 Camp David conference that paved the way for the 1979 Egyptian-Israeli peace treaty.

Carter has always maintained that Begin reneged on a pledge made at Camp David to freeze Israeli settlements in the West Bank during the interim five-year period of autonomy for its Palestinian inhabitants called for in the peace accords. But Begin vehemently maintaints that he kept the pledge he made at Camp David--to freeze settlements for three months while the details of the peace treaty with Egypt were worked out.

Since that three-month period elapsed in late 1978, the Begin government has stepped up its drive to place more Jewish settlers in the territory with the admitted aim of never allowing it to come under Arab sovereignty.

Carter openly addressed his disagreement with Begin in the February issue of Reader's Digest. In an article he coauthored with his predecessor, former president Gerald Ford, he charged that the Begin government "is not living up" to the commitments made at Camp David and "has shown little inclination to grant real autonomy to the Palestinians in the West Bank and Gaza Strip areas."

These policy differences are likely soon to be enlivened by the publication of a book by Carter's national security affairs adviser, Zbigniew Brzezinski. According to the book which will shortly be published, Carter told his wife, Rosalynn, after one particularly difficult session with Begin at Camp David that he thought the Israeli prime minister was a "psycho."

The former president and his wife were greeted by Israeli officials, but not Begin, at a formal ceremony at Ben-Gurion International Airport this morning when they arrived on a flight from Cairo.

At the airport, Carter described Begin as "a man who is searching for peace and who has exhibited great courage in the past in moving the first step toward a comprehensive peace." He also said that the hopes of the Camp David accords "have not been fully realized."

During his week-long visit to Egypt, Carter met with two representatives of the Palestine Liberation Organization, which the United States has pledge to have no dealings with so long as it refuses to recognize Israel's right to exist and with which Israel adamantly refuses to have any dealings. Carter said he found that the views of the PLO officials did not conflict with the Camp David accords but that the Palestinians remain reluctant to join peace talks based on the Camp David formula.

Carter defended the meeting, saying that as a private citizen on an unofficial trip he was free to see whomever he pleased--although he refused to identify them. The PLO named them as Ahmed Sidky Dajani, a member of the PLO executive committee, and Nabil Shaath, international affairs advisor to Chairman Yasser Arafat.