Jordan's King Hussein said tonight he will not withdraw any of his troops from the Syrian border until Syrian President Hafez Assad defuses the confrontation first by removing all his forces.

"The glass is cracked, and I don't see how it will ever be restored," Hussein said in one of his most pessimistic assessments yet of the three-week-old border crisis.

"Until the last Syrian soldier is removed from there, we will stay where we are. There are no conditions to which we have agreed," Hussein said.

In a two-hour, informal meeting with a small group of Western correspondents, Hussein ascribed an "obviously sinister motive" to the Syrian deployment of troops along the border, although he professed not to understand what specifically started the confrontation.

Hussein denied Assad's charges that Jordan has been giving covert assistance to Syrian guerrillas of the Moslem Brotherhood movement, held responsible for a wave of bombings and assassinations in Syria.

"We have suffered here in Jordan as a result of Syria's internal problems.

We have no designs for encouraging trouble here," Hussein said.

Appearing relaxed in the face of a confrontation that has put an estimated 30,000 of his most combat-ready troops along the frontier, Hussein conceded that the vital supply roads to Iraq that run through northeast Jordan could be in jeopardy as a result of the Syrian standoff.

"We may have to look at other alternatives," Hussein said. He denied that military supplies were being routed through Jordan to Iraq, although he said "other" shipments are regularly moving overland from the Gulf of Aqaba to Baghdad.

He confirmed that mediation efforts by Prince Abdullah, Saudi Arabia's second deputy prime minister and commander of the Saudi National Guard, have failed to produce any basis of compromise in the border crisis.

He specifically denied reports that Abdullah, who has traveled between Damascus and Amman, had obtained a commitment by both sides to gradually withdraw troops from the frontier.

Yesterday, while visiting the border and talking with tank and artillery commanders, Hussein mentioned to an accompanying photographer that he expected it would be his last visit there. When asked about this tonight, the king said he saw no reason to anticipate a pullback by either side.He said he had completed a series of tours to all the border positions and that there was no reason to return there as long as the crisis continued.

Discussing the issue of the Israeli-occupied West Bank, Hussein said he viewed the election of Ronald Reagan as a good omen for Palestinians. "I think we are on a new threshold. rThere is a new mandate for the United States which might pave the way to new policies," he said.

He added, "I hope the United States won't be a prisoner of past policies.

We must all free ourselves of the past constraints and perspectives."

He left no doubt that he was referring to a redefinition of U.N. Security Council Resolution 242 -- which calls for Israeli withdrawal from occupied territories but makes no specific mention of a Palestinian state.

He said he looks forward to meeting with Reagan, and predicted that Arab states, despite the conflicts arising out of the Iranian-Iraqi war, would be able to put together a unified alternative to the "bankrupt" Camp David peace process.