The Arab League ended its 11th summit here today with its goal of forging a new united Arab front shattered by the most bitter polarization among Arabs in a decade.

With radical Syria heading a boycott of six of the Arab League's 21 members while indulging in some military saber rattling along Jordan's northern border, King Hussein of Jordan, the summit host, closed the three-day meeting of kings, sheiks and presidents on a sober note of discord. He attacked Syria and some of its radical allies for supporting non-Arab Iran in its war against Arab Iraq, whose president, Saddam Hussein, played a dominant role in the summit here.

"It is a disgrace that while Iraq is fighting today to recover its rights and sovereignty over its land and waters, Iraq is being stabbed in the back by an Arab hand," King Hussein said in his closing address before the 15 Arab leaders who attended the summit. The king has become the strongest supporter of the Iraqi leader, who has forged a moderate new Arab bloc with Saudi Arabia, Jordan and the Persian Gulf states.

Only yesterday King Hussein was forced to order his 57,000-member armed forces on full alert and rush a division of his troops to the border to counter a threatening concentration of a full Syrian armored division just north of their common border. Syria, with its sophisticated Soviet-armed forces of 247,000 men, would have an edge against tiny Jordan in any eventual struggle, observers believe.

However, Jordan clearly believes it is not alone in confronting Syria and is understood to have received private assurances that its allies, notably Iraq, would come to its help if the Syrians attacked, as they did in 1970.

[In Washington, U.S. officials said Syria had deployed more than 10,000 men and 250 tanks in the border area since last weekend, Reuter reported.]

Officially, Syria opposed the summit because of its position on the two-month-old Persian Gulf war. Syrian President Hafez Assad originally called for the postponement of the summit until inter-Arab disputes over the war could be resolved. When that did not work he rallied his so-called Steadfastness Front allies -- Algeria, South Yemen, Libya and the Palestine Liberation Organization -- to boycott the summit. They were joined, under pressure from Damascus, by Lebanon.

The Persian Gulf war, however, appeared to be only an excuse for not attending the summit, Assad and his allies having found themselves increasingly isolated in the Arab world and in a distinct minority. The Arab radicals that so long dominated the area's politics have fallen under the influence of the oil-rich conservative states and the increasingly independent role of Saddam Hussein.

As the conference showed, a new, moderate, even pro-Western alliance has emerged with major implications for the future in the area.

"It has turned into a question of confrontation in the old style, sought by the Syrian group," said one senior Western diplomat here, or following the more sophisticated and moderate efforts of the Arabian alliance to gain the same end through more subtle and less dangerous use of the Arabs' new economic power.

Given this division, Arab analysts here believe, the summit may not have proved as negative as its public deliberations and communiques sounded. For while the boycott destroyed any notion of welding Arab unity, the conference brought together the majority bloc of the Arab world today with plenty of opportunities for private talks among its leaders.

Saddam Hussein, for one, succeeded in gaining a wide measure of support for his war against Iran from his fellow Arab leaders at the summit. This was reflected in the final communique, which expressed support for Iraq's efforts to recover "its territories and waters" while calling on both sides to accept a cease-fire and begin peaceful negotiations. The statement referred to Iraq's demands for certain border readjustments with Iran and the establishment of its sovereignty over the Shatt-al-Arab waterway.

Saudi Arabia's Crown Prince Fahd, another power at the summit, also put some of the finishing touches on his own plans for a Persian Gulf mutual security system. He has already sent out a series of bilateral treaties to Kuwait, Bahrain, Qatar, the United Arab Emirates and Oman. He is seeking an alliance in the region to counter the threat that Ayatollah Ruhollah Khomeini's revolution in Iran has brought home to the Saudi ruling family.

Most important, in the long run, may have been secret discussions and agreements on how to deal with the United States at a time when, some moderates feel, Ronald Reagan's landslide election could signal a major turning point in the U.S. policy toward the Arab world.

The official communiques from the summit repeated condemnation of U.S. support for Israel and criticized Washington's continued refusal to accept the PLO as the legitimate representative of the Palestinians.

But after the summit leaders had left, King Hussein gave a hint of these private discussions, although he insisted he was stating only his personal views.

While saying he had not been asked by the conference to be its spokesman or negotiator with the new Reagan administration, King Hussein said he saw its advent as an opportunity for the United States to take a "new look at all aspects of its positions and policies in this part of the world."

"It is in the United States' interest not to be a prisoner of past policies and past mistakes," Hussein said. He said he hoped the Camp David agreements, which he and most other Arab world leaders have rejected, might be replaced by a new forum for solving the Arab-Israeli conflict.

King Hussein said that although he had "no formulas" in mind, he believes that "there are meaningful opportunities on a very wide level which may enable the United States to make a just contribution for lasting peace in the Middle East."

Such remarks, coming right after the conference and in light of Reagan's already expressed desire to meet with King Hussein soon after his inauguration, were viewed by Arab and Western diplomats here as signs that the new moderate majority was indeed quietly sending signals to Reagan to encourage a new U.S. initiative in the Middle East that would be acceptable to them and would bury the already moribund Camp David agreement.