BEIRUT, Lebanon — While the eyes of the world are focused on the fading prospects of ending the Israeli-Palestinian conflict at the upcoming meeting in Annapolis, Md., an electoral deadlock in Lebanon grinds to a climax, threatening to upset an 18-year factional truce and ignite a new civil war that will add one more explosive ingredient to Middle East instability.

Lebanon's problems are rooted in the 1920s, when France's colonial regime created the country out of Syrian territory and squeezed Christians, Druze and Muslims — Sunni and Shiite — into it. At that time, the Maronite Christians were the colonial power's political allies, so the constitution that France imparted required that Lebanon's president, its most powerful official, be a Maronite. The prime minister, under the constitution, would be a Sunni Muslim and the speaker of the parliament would be a Shiite. The system, a peculiar form of democracy, is called "confessionalism."

For most of the ensuing years, confessionalism enabled the sects to coexist in a fragile balance. The enormous exception was the horrible civil war that raged from 1975 to 1989, killing 100,000 and leaving much of the country in ruins. None of the sects wants a repetition.

The current president is Emile Lahoud, an ex-general whose term expires today. For weeks, the country's political and sectarian leaders have been meeting in secret to agree on a replacement, who will have to be confirmed by the parliament in order to take office. As of Wednesday, they have failed.

Basic to the deadlock is the steady growth of the Shiite community, which is now the largest of the country's major sects. Its principal voice is Hezbollah, an organization that is political, social, religious and military. A year ago, Hezbollah's militia stopped an incursion of the Israeli army into south Lebanon, significantly enhancing its prestige across the country. But when it demanded more political power as a reward, it was rebuffed, and its ministers quit the Cabinet. Hezbollah's parliamentary representation, however, remains strong.

The U.S. position doesn't carry much weight with the Lebanese these days — mostly because of its role in Israel's invasion last year, when American officials did little or nothing to stop the incursion.

Few Lebanese — no matter what their sectarian loyalty — can forgive the U.S. role. They are reminded of it every day, by the rubble strewn across south Lebanon from repeated bombings. Although most Lebanese have grown used to America's pro-Israel policy, they are now watching with anxiety as the U.S. emphasizes Hezbollah's role as a surrogate for Iran and Syria. Lebanese have little sympathy for Iran and even less for Syria, not just because of Syria's three-decade occupation of Lebanon but also because of the recent assassinations widely attributed to Syria, notably of the popular Lebanese prime minister, Rafik Hariri.

Under Lebanese law, a presidential candidate needs to win the support of two-thirds of the parliament to be elected on the first ballot, but after that, a simple majority suffices. The U.S. strategy, as the Lebanese see it, is to promote a narrow, anti-Hezbollah majority on the second ballot.

Most Lebanese seem to be denying that civil war looms. The many private militias that were primed for battle in 1975 no longer exist, they point out. Even though Hezbollah has the strongest armed force in the country, it shows no sign of preparing for a putsch. Most Lebanese tell themselves the factions will remain stubborn until the last minute, then make a deal.

A Lebanese explosion scares the Arab world, which is already in turmoil; it should also scare Washington. At the very least, it would aggravate the Shiite-Sunni conflict in Iraq. But it also would add kindling to the Israeli-Palestinian struggle. Failure by all the factions to come together on a candidate would leave the entire region more dangerous, placing in jeopardy everyone's interests.

Milton Viorst has covered the Middle East for 40 years. He wrote this commentary for the Los Angeles Times.