Hamas has once again cast its bloody veto over any move to resolve the Israeli-Palestinian conflict; the question now is how the other players will vote. Sixteen Israelis were killed and more than 50 wounded as a suicide bomber struck at a pool hall in Rishon Letzion, south of Tel Aviv. The first such attack inside Israel in a month was timed perfectly to coincide with Ariel Sharon's Tuesday visit to the White House, where President Bush was pressing for progress toward a political solution of the conflict. Sharon, who heard the news during his meeting with Bush, flew home almost immediately, warning that the work of his West Bank offensive was not yet finished. Other Israeli spokesmen blamed the attack on Yasser Arafat's Palestinian Authority, while the PA, for its part, condemned the bombing — for which Hamas has claimed responsibility — and promised that they would "not be light-handed in punishing [the perpetrators] who have caused great harm to our cause."

No amount of PA condemnation, however, is likely to impress or restrain the Israelis. The Rishon Letzion attack was a reminder that despite Sharon's month-long offensive in the West Bank, Israelis remain vulnerable to terror strikes in their own cities. Israeli right-wingers, including former Prime Minister Benjamin Netanyahu, who is looking to eclipse Sharon, are likely to renew calls for Arafat to be banished into exile — an option strongly opposed by the Bush administration, for fear of escalating the violence and further dimming prospects for peace. But even in Washington, the latest outrage may increase political pressure on (and within) the Bush administration against restraining Sharon or pressing him back to the negotiating table.

[an error occurred while processing this directive]Sharon has maintained all along, as he did following his meeting with the President, that talk of political negotiations over Palestinian statehood is premature, and that terrorism is the primary item on the agenda right now. But the Bush administration's latest efforts are premised on the belief that Israel is unable to end Palestinian terrorism in the absence of moves to end its occupation of the West Bank and Gaza and create a viable Palestinian state. Israel reserves the right to continue mounting punitive and preventative operations inside PA territory as long as violence continues; the Palestinians and their Arab backers insist that continued Israeli incursions preclude a cease-fire and a crackdown on terrorism. Moreover, the Israeli offensive has left the PA's own security structures in tatters — a fact acknowledged in President Bush's announcement Tuesday that CIA director George Tenet would be sent to help the PA rebuild a single, consolidated security force to facilitate a cease-fire. But a renewed Israeli offensive may render that idea a non-starter, leaving the White House back where it started three weeks ago.

The Bush administration agrees with Sharon — and with most Palestinians — on the need to transform the PA from Arafat's corrupt and authoritarian personal fiefdom into a more transparent, accountable and democratic body. But all have different ideas of what this may mean in practice. The Israelis want, primarily, to be rid of Arafat in the belief that an alternative leadership may be more inclined to accept Israel's terms. The Americans want good governance and an end to terrorism. And the Palestinians want to keep Arafat in power, but as the leader of an entity truly representative of the will and interests of its citizenry — and therefore in all likelihood less rather than more amenable to the sorts of deals Arafat has embraced, however deceitfully, in the past.

The extremists of Hamas, meanwhile, know they have nothing to gain and plenty to lose from any new Israeli-Palestinian truce, and have therefore revived their traditional tactic of dispatching suicide bombers to put a stop to any dialogue. That's a direct challenge to Arafat's authority, because he and his officials have made abundantly clear to Palestinian militants in recent weeks that further attacks inside Israel right now will force the PA to launch a Palestinian civil war.

The Rishon Letzion attack, and the likely Israeli response, highlights the depth of the challenge facing the Bush administration's Mideast policy. Terror attacks allow Sharon to postpone the drive for a political solution; Israeli military responses create the excuse for Arafat to postpone the showdown with Palestinian militants required by any truce. The problem for Washington is that allowing the bloody impasse to continue imperils wider American objectives in the region and beyond. And yet the administration's own policy is far from coherent, as the relentless competition between the State Department and hawks led by Defense Secretary Rumsfeld results in continued mixed messages. Having resolved to reluctantly reenter the fray to protect its wider interests, the political cost of returning to the sidelines may have become prohibitive. One unintended consequence of the latest Hamas outrage, then, may be to draw the Bush administration even deeper into the Mideast political quagmire than it had ever intended to go.