WASHINGTON--President Reagan said yesterday that Soviet leader Mikhail S. Gorbachev may want to conclude a U.S.-Soviet long-range missile treaty this year to avoid having to negotiate with a new U.S. administration.

While acknowledging that "none of us really think" such a strategic missile deal could be completed at the coming summit in Moscow, Reagan said he did not think Gorbachev necessarily wants to take his time.

In a wide-ranging interview with foreign broadcasters, the president also maintained again that the clandestine sales of arms to Iran did not amount to an arms-for-hostages deal and said the Soviet Union should resume diplomatic relations with Israel if it wants to take part in an international peace conference on the Middle East.

Asked whether he was worried about the impact on the May 29-June 2 summit of recent reports of astrological influences on White House affairs, Reagan replied:

"Well, I hope that Mr. Gorbachev has heard some of the things that I have been saying about those charges, because no decision was ever made by me on the basis of astrology."

In the question-and-answer session in the Oval Office, the president said he thought Gorbachev should be encouraged in the reforms he is pushing in the Soviet Union. "I think it is evident that he is running into opposition, that there are those who want to cling to more of the Stalinist policies," Reagan said.

"If there's any way that outside nations could be helpful in this, they should," he said, "because many of the reforms that he has undertaken are aimed at the things that we have always criticized in the Soviet Union. And if there is a way to be helpful in that, certainly, to at least acknowledge our approval of what he is doing, that we should do that."

Previewing the summit in Moscow, Reagan said he hoped more progress can be made in the area of human rights, and that the Kremlin still has not lived up to promises made in the Helsinki accords on that subject.