The president appointed Harvard-educated billionaire businessman and former premier Najib Mikati as prime minister-designate after a majority of lawmakers voted for him. Mikati defeated U.S.-backed Saad Hariri, who was prime minister from 2009 until Hezbollah forced the unity government he led to collapse two weeks ago.

"My hand is extended to all Lebanese, Muslims and Christians, in order to build and not to destroy," Mikati said after he was chosen, striking a conciliatory tone and calling for another unity government.

The vote caps Hezbollah’s steady rise over the past few decades from a resistance group fighting Israel to Lebanon’s most powerful military and political force. The shift in the balance of power drew warnings from the U.S. that its support for Lebanon could be in jeopardy, demonstrating the risks of international isolation if Hezbollah pushes too far.

Many fear Lebanon’s political crisis could re-ignite sectarian fighting similar to Shiite-Sunni street clashes that killed 81 people in Beirut in 2008. Hezbollah’s rise also looked likely to also raise tensions with Israel, which borders Lebanon to the south. Hezbollah and Israel fought a short but devastating war in 2006.

Despite opposition from the Hariri camp, Mikati is seen as a relatively neutral choice who enjoys good relations with both Syrian President Bashar Assad and with Hariri. That puts Hariri in the awkward position of rejecting a candidate who has been an ally in the past.

Hariri’s bloc has insisted it will not join a government led by a Hezbollah pick, which could mean months of political deadlock ahead in Lebanon.

According to Lebanon’s power-sharing system, the prime minister must be a Sunni, the parliament speaker a Shiite and the president must be a Christian Maronite. Each faith makes up about a third of Lebanon’s population of four million.

Because Mikati is a Sunni, protesters accused him of being a traitor to his sect and betraying Hariri.

Sunnis demonstrated for a second day across the country, in Beirut and along the main highway linking the capital with the southern port city of Sidon.

But the largest gathering Tuesday was in the northern city of Tripoli, a predominantly Sunni area and a hotbed of fundamentalists where thousands of people converged at a major square. Protesters attacked a van of Al-Jazeera television, accusing the Arabic satellite station of bias in favor of Hezbollah. The station said no one was injured.

A senior military official said several armed men fired in the air in west Beirut, but the army intervened and dispersed them. Soldiers also clashed with demonstrators in the town of Naameh, south of Beirut, and two civilians were wounded, security officials said.

But besides the large protest in Tripoli, the gatherings were mostly localized and not hugely disruptive.

After it was clear that Mikati won the support of a majority of lawmakers Tuesday, Hariri thanked people for their support but called for restraint.

"I understand your emotions … but this rage should not lead us to what is against our morals, faith and beliefs," he said.

Hezbollah brought down Hariri’s Western-backed government on Jan. 12 when he refused the group’s demand to cease cooperation with a U.N.-backed tribunal investigating the 2005 assassination of his father, former Prime Minister Rafik Hariri.

Hezbollah, which denies any role in the killing, is widely expected to be indicted.

Hariri has stayed on as caretaker prime minister.

Hezbollah can now either form its own government, leaving Hariri and his allies to become the opposition, or it can try to persuade Hariri to join a national unity government. In a speech Sunday night, Hezbollah leader Sheik Hassan Nasrallah said he favored a unity government.

Hariri said Monday he will not join a government headed by a Hezbollah-backed candidate. Hariri’s Future bloc declared a day of peaceful protests Tuesday — but called it a "day of rage" and played on the sectarian dimension of the conflict.

The United States, which has poured in $720 million in military aid since 2006, has tried to move Lebanon firmly into a Western sphere and end the influence of Hezbollah, Syria and Iran.

State Department spokesman P.J. Crowley warned Monday that continuing U.S. support for Lebanon would be "problematic" if Hezbollah takes a dominant role in the government, though he declined to say what the U.S. would do if Hezbollah’s candidate becomes prime minister.

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Associated Press writers Elizabeth A. Kennedy and Zeina Karam contributed to this report.