Jordan's King Hussein today virtually ruled out the possibility of joining any peace talks with Israel unless the United States sharply increases pressure on the Begin government to modify its stance on West Bank settlements and to withdraw from Lebanon.

Meeting with reporters, Hussein discussed his position in considerable detail, saying, "Current Israeli attitudes are most discouraging," and "American credibility is passing through a difficult test."

Later, Hussein met with Philip C. Habib, U.S. special Middle East envoy, who reported on last week's Washington visit by Israeli Foreign Minister Yitzhak Shamir and a Lebanese delegation headed by Foreign Minister Elie Salem. Habib also was said to be probing for any flexibility of Hussein to join talks with Israel.

There appears to be little, if any movement on that score, judging from Hussein's public comments, although he did indicate he may have a more definitive statement to make soon. "Within a few days," he said, "we will know where we stand."

Hussein confirmed he would have "critical talks" in Amman sometime this week with Palestine Liberation Organization leader Yasser Arafat about prospects for the king to serve as a spokesman for Palestinian interests in negotiations with the Israelis. But the likelihood of meaningful progress toward such negotiations appeared to be very slight, whatever the outcome of the Hussein-Arafat meeting.

"Israel has not contributed in any form" toward opening the way for talks to resolve the issue of a Palestinian homeland, Hussein said. "Whereas the Arab position is positive, the Israeli position is negative."

The king repeated his qualified "welcome" of the Reagan administration's proposal for establishment of a Palestinian entity on the West Bank and Gaza Strip in association with Jordan. But he emphasized that the United States has failed thus far to create conditions whereby the Reagan plan could serve even as a starting point for negotiations.

"Unfortunately," Hussein said, "the facts are we are way behind schedule on the American side in terms of the goals set for the beginning of this year: total withdrawal of foreign forces from Lebanon." He also criticized American failure to stop Israel from creating new settlements on the West Bank, which he asserted had doubled since last September.

Unless the United States can make headway on these two matters with Israel, "it is obvious" that talks on a broader settlement cannot get started. "We are hoping that the United States will contribute towards enhancing its credibility" by pressing Israel for concessions, he said.

Hussein was in Londonas head of an Arab delegation meeting with British officials.

Last fall, the king was to have led an Arab League delegation here for similar meetings, but they were called off because of British Prime Minister Margaret Thatcher's refusal to meet with any PLO officials. Hussein went out of his way in praising the British today, stressing that the strains caused by that dispute are over. A leading Palestinian academic, who is not a member of the PLO, was included in the Arab league team.

Britain's Foreign Secretary Francis Pym and other government spokesmen, commenting after the talks yesterday, expressed sympathy for the Arab stance. The net effect of the meetings was to underscore Britain's "tilt" toward the Arab side in the Middle East conflict, British sources acknowledged, primarily because of what is regarded here as Israeli intransigence on the Lebanon withdrawal and settlements issues.