WITH his entire Middle East policy on the line, President Clinton is determined to do all he can to prevent terrorist bombs from blowing apart the best opportunity in 50 years to put the Israeli-Arab conflict to rest.
The main task of containing the unprecedented terrorist assault by the Palestinian militant group Hamas will fall to Israel. But for now the US can do more than provide moral support.
The US is taking a three-pronged approach by sending bomb-detection equipment to Israel, rallying diplomatic support for the peace process, and attempting to isolate Hamas.
The US has ''clout with the sponsors of Hamas: Iran'' says Geoffrey Kemp, a Middle East specialist at the Nixon Center for Peace and Freedom, in Washington.
The way to pressure Iran, says Mr. Kemp, is to demonstrate to its creditors, including Germany and Japan, that ''the mullahs are up to no good.'' That means continuing US efforts to persuade Iranian creditors to close off lines of credit and to stop rescheduling existing debts.
At the same time, Clinton is urging all sides to remain engaged in the peace process, despite the bombings.
Clinton has written to Syria's President Hafez al-Assad, urging that he condemn the latest terrorist attacks.
In addition to the measures announced Tuesday, supporters of Israel are pressing for passage of domestic antiterrorism legislation that would prohibit fund-raising for Hamas in the US, and legislation that would expand existing sanctions on Iran by placing sanctions on foreign firms investing in Iran's energy sector.
''There's no silver bullet the US can supply that will stop terrorism in Israel, but these bills could rob Hamas of the funds they need to survive,'' says one Washington-based Middle East expert.
The US and Israel already have significant antiterrorist cooperation, adds a US official. ''The new effort will increase cooperation by providing equipment, logistical assistance, forensic assistance, and enhanced intelligence exchange.''
Analysts presume that Israel is better informed about Hamas and other Middle Eastern terrorist groups than is the US. Even so, there may now be more sharing of information between the two countries, a fact that worries some experts.
''We're so anxious for peace to blossom that we may not be thinking through where this will all lead: to terrorism in the US,'' says Robert Kupperman of the Center for Strategic and International Studies in Washington.
''Any public dimension of US support for Israel would have to be weighed against the background of Hamas's ability to strike against the US,'' adds another leading Middle East analyst, also based in Washington. ''But this administration has such a stake in Middle East peace, and Hamas terrorism has become such a threat to that peace, that we would have to do whatever we could to help Israel contain Hamas to salvage the peace process.''
Hamas was founded in Gaza in 1987. It organized with the acquiescence of the Israeli military, which then governed the territory and viewed Hamas as a counterweight to Yasser Arafat's Palestine Liberation Organization (PLO).
Hamas is said to have a presence in Syria, Lebanon, Jordan, Sudan, and Yemen, as well as the West Bank and Gaza, though its operating funds are believed to come mostly from the Iranian government and from religious organizations in Saudi Arabia.
In addition to terrorism, Hamas is actively administering social-welfare programs in Gaza and the West Bank, including economic assistance, health care, and education.
Various relief organizations in the US channel money to schools and orphanages run by Hamas. Critics say this frees up money for Hamas to use for less-benign purposes.
Support for Hamas among West Bank and Gaza Palestinians dropped after Israeli troops began pulling out of the two territories, as promised in an Israeli-Palestinian accord signed last year. Hamas resumed its attacks after the death of Yehiya Ayash, a Hamas terrorist who was killed by the Israeli secret service in January.
On Tuesday, Israel rejected a truce offer from the military arm of Hamas. In a fax, the group promised to call off further attacks until July if Israel refrained from retaliation.