BEIRUT, Lebanon — They were lawyers in black court robes, doctors in white coats, businessmen, housewives and students. They shouted, waved flags and handed red roses to soldiers.

The 25,000 protesters who massed outside Lebanon's Parliament yesterday and yelled, "Syria out!" didn't get all they wanted; Syrian President Bashar Assad said in an interview published yesterday that withdrawal of 15,000 Syrian troops would not come immediately, and even then, with strings attached.

But the dramatic display of defiance — reminiscent of Ukraine's peaceful "Orange Revolution" and broadcast live across the Arab world — forced out Lebanon's pro-Syrian prime minister and Cabinet, two weeks after the assassination of an opposition leader.

Minutes after Prime Minister Omar Karami said he was stepping down, jubilant demonstrators demanded that Syrian-backed President Emile Lahoud bow out, too.

Syria remained silent yesterday about the rapidly changing atmosphere in Beirut, where it ruled unopposed for years — even deciding on Lebanon's leaders — after deploying troops, supposedly as peacekeepers, during the 1975-90 civil war.

MARCO DI LAURO / GETTY IMAGES Protesters carry Neamatallah Naser, a member of the Lebanese Parliament, after he broke through the line of soldiers that tried to prevent citizens from participating in yesterday's demonstration outside Parliament in Martyrs' Square.

But in one sign Syria has no intention of packing up and leaving, Assad said there will be a price for Syrian troop withdrawal: a settlement with Israel.

"Under a technical point of view, the withdrawal can happen by the end of the year," Assad told the Italian newspaper La Repubblica. "But under a strategic point of view, it will only happen if we obtain serious guarantees. In one word: peace."

The developments in Beirut could provoke a strong military response from Syria. It also could plunge Lebanon, a nation of 3.5 million, back into a period of uncertainty, political vacuum or worse.

The White House welcomed Karami's resignation, saying it opens the door for new elections that are "free of all foreign interference" from Syria, but calling again on Syria to pull out its soldiers.

"Syrian military forces and intelligence personnel need to leave the country," White House spokesman Scott McClellan said. "That will help ensure that elections are free and fair."

Karami's government may have stepped down, at least in part, in hopes of quelling the unprecedented anger at Syria and its allies in Lebanon. Despite the resignation, Syria remains the major player in Lebanon: Aside from its troops, it has powerful allies, including the president, the intelligence services and the military.

Omar Karami: "May God preserve Lebanon."

Still, the resignation of Karami and his government appeared to be a huge victory for the opposition, united by dislike of the Syrians and the Syrian-backed government, and by the drive to find those who killed former Prime Minister Rafik Hariri two weeks ago. Many blame Syria for his assassination.

A series of protests has shaken Lebanon since Hariri, a billionaire businessman and the nation's most prominent politician, was killed by a bomb in Beirut on Feb. 14. Sixteen others also died.

President Lahoud quickly accepted the resignation of Karami's 4-month-old Cabinet — which replaced Hariri's government — and asked Karami to stay on in a caretaker capacity until a new government is formed.

But opposition leaders — a diverse group of Muslims, Druze and Christians — demanded a neutral government to organize parliamentary elections this spring and to investigate Hariri's slaying.

Druze opposition leader Walid Jumblatt, responding to Assad's published remarks, said Lebanon "cannot wait for peace to be achieved" in the Middle East and demanded a speedy troop withdrawal.

However, opposition lawmaker Ghattas Khouri called for more patience. "The battle is long, and this is the first step, this is the battle for freedom, sovereignty and independence," he said.

Like their counterparts in Ukraine, the Lebanese demonstrators took their ground and held it; they planned to stay in Beirut's central Martyrs' Square again last night. And like Ukraine, their movement had trademark colors: the bright red and white of the Lebanese flag, waved high in the air or worn as a scarf.

A day earlier, Lebanese Interior Minister Suleiman Frangieh announced a ban on all demonstrations, and hundreds of soldiers and police ringed Martyrs' Square yesterday. But there was no violence, even as more protesters evaded the cordon and joined the demonstration.

Protest leaders urged followers not to provoke security forces, and some security officers appeared to sympathize with the illegal demonstration.

Protesters gave red roses to some soldiers, sang the national anthem and chanted: "Syria out!" and "We want no other army in Lebanon except the Lebanese army!"

In announcing his resignation, Karami said he did it for the good of Lebanon.

"I am keen that the government will not be a hurdle in front of those who want the good for this country. I declare the resignation of the government that I had the honor to head. May God preserve Lebanon," Karami said in remarks heard through loudspeakers and watched on a giant screen by throngs in Martyrs' Square.

Demonstrators immediately shouted for Lahoud to step down. "Lahoud, your turn is coming!" the crowd shouted.

Lahoud's six-year term was renewed in September by Parliament, under apparent Syrian pressure, in defiance of a U.N. resolution that demanded presidential elections and the withdrawal of Syrian troops.

Material from The Washington Post and Christian Science Monitor is included in this report.