The Reagan administation sought yesterday to dispel the impression that it is now ready to participate in a Middle East international peace conference attended by the Soviet Union.

In the process, the administration made clear that there are still fundamental differences between the United States and King Hussein of Jordan over the framework for holding new peace talks despite initial hopes of a breakthrough after the king's meeting Wednesday with President Reagan.

At the same time, White House spokesman Larry Speakes said the administration remained ready to consider an international conference if "it would lead to direct talks between Jordan, Palestinians and Israelis."

A State Department spokesman said the United States continued to have "major difficulties" with the idea of holding a conference that would include the Soviet Union, and emphasized that no agreement had been reached yet on "a mechanism" for conducting direct Arab-Israeli talks.

Speakes refused to reject the idea of Soviet participation, but noted that "their agenda for the Middle East is quite different from ours."

Reagan, in reply to a question after his meeting with the king at the White House Wednesday, refused specifically to rule out such a conference, saying "we're still discussing this whole matter."

This remark encouraged speculation that the United States was shifting its position on Soviet participation at a conference in response to the king's announcement that the Palestine Liberation Organization was now ready to recognize and negotiate directly with Israel.

Then later Wednesday, U.S. officials said the United States might be prepared to drop its opposition to the holding of new peace talks under "the umbrella" of such a conference.

These comments were sufficient to stir a vehement Israeli protest, prompted by Israel's concern that Washington was indeed changing its longstanding opposition to the holding of a conference that the Soviets would attend.

Israeli Prime Minister Shimon Peres, on a visit to the northern coastal city of Acre, denounced the idea as "an attempt to sidestep the need for direct negotiations" with Israel.

Yesterday at the daily noon briefing, State Department spokesman Edward Djerejian was repeatedly asked for a clarification of the U.S. position on the international conference.

In seeking to do so, Djerejian inadvertently further confused the issue by saying at one point that the United States would "welcome" any sign that the Soviet Union was ready to play a "constructive role" in the Middle East peace process.

Djerejian quickly added that Washington saw "no evidence that the Soviets are prepared to play such a role" and listed six specific actions it would regard as constituting "constructive behavior" on Moscow's part. These included resuming full diplomatic relations with Israel, ending Soviet anti-Semitic propaganda, improving the treatment of Soviet Jews and ending arms aid to militia groups in Lebanon.

United Press International reported Djerejian's comments as a statement of U.S. conditions for the acceptance of Soviet participation at a Middle East peace conference.

Later, however, another State Department spokesman said the six steps concerned U.S. acceptance of a new Soviet role in Middle East developments generally, and had nothing to do with its participation in an international conference, to which Washington was still opposed.

The spokesman also explained that what the United States understood currently by an "international conference" was one in which Israel, Jordan, the Palestinians and possibly Egypt and the United States would participate but not including the Soviet Union or a large number of other countries.

King Hussein has said that an international meeting should be attended by all five permanent members of the U.N. Security Council, including the Soviet Union and China.

The U.S. spokesman said the United States fully understood that the king needs an international "cover" or "umbrella" to permit him to go forward with direct Arab-Israeli talks involving a joint Jordanian-Palestinian delegation.