JERUSALEM, FEB. 13 -- The Israeli government is planning to build 12,000 homes for new Jewish settlers in the occupied West Bank and Gaza Strip in a three-year program that would increase the Jewish population of the territories by more than 50 percent, two opposition members of parliament said today.

The legislators, who said they had obtained internal plans of the Construction and Housing Ministry, charged that the building program violated guarantees given by the government of Prime Minister Yitzhak Shamir to the Bush administration in exchange for $400 million in loan guarantees for housing construction.

Shamir's government, which is now seeking $10 billion more in loan guarantees from Washington, promised last fall that it would not build housing in the territories for the hundreds of thousands of Soviet immigrants now coming here. It also pledged not to direct the immigrants to settlements and said it would provide the State Department with information about any settlement construction.

However, leftist legislators Dedi Zucker of the Citizen's Rights Movement and Chaim Oron of the Mapam Party said in a three-page report that about 2,500 Soviet immigrants already are living in occupied territories outside Jerusalem. They suggested that more Soviets would surely move to such areas if the new housing were built. The immigration wave has caused a severe housing shortage in Israel, and Soviet arrivals already are virtually forced to settle wherever apartments are available.

Zucker and Oron charged that the government building program, which they said would cost $750 million over three years, "has the aim of creating facts on the ground that will make it difficult for Israel to enter the political process that is expected after the Persian Gulf War."

They said the building program is already underway and that the government is putting 1,000 mobile homes into Jewish settlements in the Arab territories.

At least 90,000 Jewish settlers are now estimated to live in about 140 communities scattered through the West Bank and Gaza Strip, which are home to 1.7 million Palestinians. The Bush administration, which says Israel should trade captured land for peace with its neighbors, strongly opposes further Jewish settlement of the territories. The issue contributed to a sharp deterioration in U.S.-Israeli relations over the two years before the gulf crisis.

A spokesman for the Housing Ministry, which is headed by Ariel Sharon, a hard-line leader of the Likud Party, did not respond today to several inquiries about the opposition report. A senior adviser to Shamir, Avi Pazner, said the report "sounds far-fetched" but added that he did not know whether it was correct.

Since the formation last June of Shamir's present cabinet, which includes far-right nationalist and religious parties, the government has refused to make its plans for settlements public, although it has said settlement of the territories would continue.

In recent weeks, sources here said, officials in Jerusalem have been at odds with the State Department over U.S. attempts to obtain the promised information about settlements. U.S. officials recently complained that Israel's answers to questions about its settlement policy were inadequate, officials here said.

Aides to Shamir say the government responded that, in its view, it had provided the State Department with all the information it requested. However, officials said, the $400 million in loan guarantees linked to the information request has still not been released by Washington, a delay that Secretary of State James A. Baker III recently attributed to "technical problems."

Israeli commentators say the continuing problems with the housing money -- which is only a fraction of what Israel hopes to obtain from the United States -- reflect the deep tensions that still underlie the wartime patina of cooperation between the United States and Israel.

The legislators' report said the Housing Ministry plan for settlement construction extended from the present budget year, which ends in March, to 1993. For this year, it said, the government has allocated 2,149 new homes to settlements, of which some will be built directly by the government and some financed through purchase guarantees to private builders.

According to the report, the overall plan places priority on adding homes to existing settlements, "to assure that the present claim made to the Americans can be perpetuated: that no new settlements are being constructed."