President Carter's iron determination to reconvene the Geneva Mideast peace conference before the end of this year has been subjected to secret and agonized warnings from Arab governments ever since Secretary of State Cyrus Vance's first journey of shuttle diplomacy last February.

These warnings, undisclosed until now, came principally from Syria. Lebanon and Jordan. They were given to Vance before President Carter made his final decision to press on to Geneva in 1977 - in short, at a time the Arabs felt they could still influence his plans and timing.

In February, Vance was told of this Arab fear: that, much as the Arabs wanted a settlement with Israel. Carter was courting "an explosion" in the Middle East if he pushed or cajoled the parties to Geneva without the framework of an agreement.

Vance listened. On his return to Washington, the Arab warnings were studied and rejected. Israel and the Arab states were soon informed that U.S. persuasion - and pressure - would be directed toward one objective: Geneva by the end of December.

"Your President has an obsession about getting to Geneva," one authoritative and highly respected Arab leader, here for the U.N. General Assembly, told us. That "obsession," as seen by the Arabs, is fueled by the President's need to show momentum in his praiseworthy drive toward a political settlement to end 30 years of war in the Middle East.

Carter is perceived as genuinely worried that his credibility as a world leader would suffer both here and abroad if he failed to bring off his first major foreign undertaking. That, of course, is getting the long-recessed Geneva conference started up again.

But the Geneva goal is worth achieving. Arab leaders feel, only if there is a "reasonable expectancy" of settling the major issues dividing the Arabs and Israel once the reconvened conference gets under way.

Instead, the President's diplomacy has been mainly directed at procedural obstacles, only marginally at the hard-rock issues that block real settlement.

Thus, Arab leaders warned about this dangerous sequence of events if Carter does in fact persuade the four Arab states - Egypt, Syria, Jordan and Lebanon - to come together in Geneva with Israel. (They agreed on Tuesday to attend.)

First, virtually certain deadlock on the big unresolved issues some kind of Palestinian state as demanded by both the Arab countries and the Palestine Liberation Organization, final borders between Israel and its neighbors and conditions of peace with Israel.

Second, a rise of Arab radicalism in Egypt and Syria as the hard issues fail to move toward resolution and the illusion that Geneva itself automatically will lead to settlement begins to fade.

Third, a renewal of PLO guerrilla warfare against Israel, with southern Lebanon once again becoming a bloody battleground between PLO nationalists and the shaky government of Lebanon.

Underlying all this is Arab fear that once the Geneva conference is reconvened, U.S. pressures on Israel will confront Carter with devastating political counterpressures in the United States, with Israel shielded by its agreement to go to Geneva.

Defenders of Carter argue that these volatile political ingredients will be as dangerous if Geneva is not reconvened. But the Arabs strongly disagree. The attainment of a new Geneva conference, they believe, is certain to have the effect of raising expectations far beyond the realistic level, and when the illusion of progress is pierced, the reaction will be devastating.

These Arab fears may prove to have been overstated if, as Carter greatly hopes, the peace conference is convened and does in fact spark new momentum toward settling the real issues. That is what the President and his advisers are counting on.

But even so, the Arab fears rejected by Carter carry a different kind of warning for the President. Despite nine months of nonstop effort to settle the Arab-Israeli struggle, he has failed to gain the confidence of the Arabs. They praise his objectives but are fearful of his tactics.