Amman — Israel's leaders may be worried about Jordan getting sophisticated missiles and jets from the United States.
But Jordan's rulers have very different concerns.
And among the things currently worrying them the most is the theory that because Jordan has so many Palestinian inhabitants it already is the Palestinian state in the Middle East.
The so-called ''alternative Palestine theory'' is often heard in Jerusalem and among Reagan administration Middle East specialists. It is most frequently propounded by Israeli Defense Minister Ariel Sharon (and supported by Israeli government pamphlets).
Jordanian Crown Prince Hassan sees the theory as an argument aimed at trying to destabilize the government of his brother, King Hussein, and other Arab states where sizeable Palestinian populations reside: Lebanon, Kuwait, and Syria.
Moreover, he contends that Israel is trying to shift attention away from the West Bank -- where 800,000 Palestinian Arabs live -- while causing structural changes that incorporate the occupied territory more and more into Israel.
The crown prince specializes in West Bank matters and is akin to a vice-president in royal authority. He says he fears Israel is preparing ''in three years or less'' to stimulate ''a major exodus of Palestinians from the occupied territories, whereby they (Israeli settlers) become numerically superior.''
Crown Prince Hassan criticizes the US for adhering so firmly to the Camp David agreements that it is unable to arrest the ''Israelization'' of the West Bank and Jerusalem.
By sticking to Camp David, he argued in an interview with the Monitor, the US sanctions a situation in which:
* ''There is no discussion of land, but a continuous change in the status of land in the occupied territories.''
* ''No discussion of settlements, except nominally, while in fact the settlements as we know continue to be expanded.''
* ''No discussion of water but a continuous grabbing of water to serve the Israeli population of the West Bank.''
Jordanian leaders say they are not concerned the 1.5 million Palestinians (of a total population of 2.6 million) will rebel against the monarchy.
Most Palestinians contacted by this correspondent over the course of a week express relative satisfaction with the 12-year-old social pact in which Hussein rules but Palestinians control most of the business sector.
But diplomats here say there still is concern among Jordanian leaders that the ''alternative Palestine theory'' could one day be seized upon by some sectors of the population -- especially if the monarchy somehow makes a diplomatic misstep, such as initiating a separate peace with Israel.
''For us as a host country,'' says Prince Hassan, ''we cannot move into a situation of saying this is the alternate homeland for the Palestinians because we would be destroying the raison d'etre of the Palestinian cause.''
But by frequently asserting that Jordan and other countries represent the ''new Palestine,'' says Hassan, Israeli leaders ''actually are saying that this refugee population should make a home of its own by destablizing governments in neighboring states.
''The cherished prize of any (Israeli) military planner is to have a psuedo-radical neighbor whom he can use as the whipping boy,'' the crown prince says.
Other Jordanian officials accuse Israel, Syria, and Iran of pursuing similar goals of trying to undermine the Arab moderates (Jordan, Saudi Arabia, the Gulf states, and Iraq). These accusations have increased since Jordan began forming a volunteer force to fight alongside Iraq in its war with Iran.
''Israel is trying to hem us in,'' the crown prince says. By aiding Iran and rejecting peace overtures such as the eight-point Saudi peace plan, Hassan says, Israel is seeking ''to create a mosaic out of the Middle East, to Balkanize it, with Israel as primus inter pares (first among equals).''