THE resettlement of Soviet Jews in Israel is an issue of great humanitarian concern. The United States, through pressures on Moscow and through its own immigration policies, helped ensure the flow of people to Israel. Washington, therefore, has responsibilities in this matter.But those responsibilities don't include immediate approval of the $10 billion in loan guarantees requested by the government of Prime Minister Yitzhak Shamir last Friday. Secretary of State James Baker rightly points out that the aid request, which would make it easier for Israel to get housing-development loans on the commercial market, could thwart progress toward a crucial Middle East peace conference this fall. The 120-day delay requested by President Bush makes sense; Congress should support it. If the loan-guarantee package is granted with no assurance that Israel will curb its settlement program in the occupied territories, US credibility as a mediator in Arab-Israeli negotiations could be shot. It's not that Soviet Jews are resettling in large numbers in the territories. They're not. But so long as current Israeli policy remains, what's to keep fresh development funds from serving as a means of bolstering the generous incentives offered people willing to settle in the West Bank or other areas ? Arab parties to the proposed talks consider US action to halt the settlements a critical test. On the other hand, Mr. Shamir sees the delay as a cave-in to Arab demands and a blow to US credibility. If the choice is between loan guarantees or an end to settlement expansion, Israel's leadership could decide the price is too high and opt out of negotiations. What should the US do? Reaffirm its position that continued Jewish settlement of the territories undermines the chances for lasting peace. Affirm that it is committed to help resettle Soviet Jewish immigrants within Israel and will do so with renewed enthusiasm once peace talks are begun. Ultimately, there may be no greater inducement for new arrivals to settle permanently in Israel than freedom from the violence and war that have stunted development in the region for decades.