Mark A. Siegel, who until last week was President Carter's chief White House link to the American Jewish community, has decided to resign from the White House staff because of his disagreements with the administration's Middle East policy.

Siegel drafted his letter of resignation yesterday. It was not made public by the White House because the president asked to see Siegel today before the resignation is officially announced.

Although the letter was not made public, it was learned that Siegel's decision to resign was triggered by his disagreement with the administration's proposed Middle East arms sale package involving the supplying of warplanes not only to Israel but to Egypt and Saudi Arabia.

Moreover, Siegel was said to believe that he had been provided misleading information about the proposed sale of sophisticated F15 fighter planes to the Saudis by Zbigniew Brzezinski, the president's national security affairs adviser, and the National Security Council staff.

An official announcement of Siegel's resignation was expected yesterday but was not made.In the afternoon, Siegel met with his immediate superior, White House political adviser Hamilton Jordan, as well as presidential press secretary Jody Powell and others. It was then that the announcement was delayed.

However, Siegel's intentions did not appear to be in doubt. In an interview yesterday, he confirmed the resignation plans and said he was not being forced out of the White House.

"It was my decision and Hamilton agrees," he said.

Earlier in the day, Powell left no doubt that Siegel's future at the White House was in question.

Where we go from here, I can't answer," he told reporters. "We're trying to figure out what is the best thing to do. . . We're trying to figure out the decent course of action."

By the end of the day, all Powell would say was "I have nothing to add."

Siegel's future at the White House became a major question mark when it became known Tuesday that last week he informed Jordan that he would no longer serve as the White House liaison with Jewish groups.

Siegel voted his disagreement with the Middle East arms sale package and his belief that while he was expected to defend the president's policies before Jewish groups he had no meaningful role in developing those policies within the White House.

At the time of his March 1 meeting with Jordan, Siegel asked to be assigned to new duties on Jordan's immediate staff. But in the days since then, he changed his mind, finally concluding that he could not serve Carter effectively in any capacity.

Jordan informed the president Tuesday of Siegel's intention to resign, and Carter, at least then, made no attempt to prevent it.

Siegel's planned resignation comes at a critical, time in the Middle East peace negotiations process. It also represents the first public rupture in the Carter administration, where public disagreements among aides are not tolerated by the president or his immediate assocates.

The administration will send its Middle East arms sales proposals to Congress early next month, when it is expected to set off an emotion-charged debate. Carter's insistance that the sale is a "package"-and that Israel will be denied additional warplanes if the sales to Egypt and Saudi Arabia are blocked - has mobilized Israel's strongest supporters against the president.

Moreover, next week Carter is to meet in Washington with Israeli Prime Minister Menachem Begin and is expected to press Begin for concessions on the issue of Jewish settlements in occupied Arab territories.

Although the arms sale was the catalyst, Siegel's decision to resign was the culmination of months of misgivings over the direction of the administration's policy in the Middle East.

For months, Siegel has been bombarded with complaints from his Jewish contacts about those policies. He has also harbored a deep distrust and dislike for Brzezinski, believing Brzezinski to be responsible for what he considered a drift away from total U.S. support of Israel.

The 31-year-old Siegel, a former executive director of the Democratic National Committee, is one of the two or three most politically liberal members of the White House staff. He had other disagreements with Carter on matters of policy. But Israel's survival is a deeply emotional commitment of Siegel's, the one issue, he has told friends, that would cause him to break publicly with the president.

He has acknowledged that he cannot be "neutral" about the Israeli cause and he considered himself the only strongly pro-Israeli adviser around Carter.

What caused Siegel to change his mind since last week about staying on the White House staff was not clear yesterday. In recent conversations with friends, he has referred to himself as "a lone voice of dissent on a matter of conscience," strongly suggesting that there is little room for disagreement in the Carter White House.

Siegel's resignation clearly will deepen the division between the administration and the American Jewish community. One sign of their strained relationship was the confirmation yesterday that a $1,000-a-plate Democratic Party fund raiser scheduled for May 22 in New York has been postponed until December because of fears that Jewish contributors would boycott it to protest Carter's Middle East policies.