Syria quickly condemned the attack as a "criminal act." The Foreign Ministry said in statement that Damascus "affirms its sympathy and solidarity with brother Lebanon in the face of all those who are manipulating its security and stability."

The immediate denunciation came in time to dispel any suspicions or accusations by anti-Syrian Lebanese groups of Damascus' responsibility in the blast, which could tarnish Suleiman's talks with Syrian President Bashar Assad before they even start, analysts say.

The Lebanese army said it believed it was the target of the bomb, planted in a bag at a military gathering point in the busy Masarif Street commercial district and exploded during morning rush hour near a bus carrying off-duty Lebanese soldiers.

Nine soldiers and five civilians were killed, and at least 40 others were wounded.

In a statement, Suleiman, who was army chief until his election by parliament in May, condemned the blast as a "terrorist crime," vowing that "the army and security forces will not be terrorized by attacks and crimes that target it and civil society, and the history of the army attests to that."

No one claimed responsibility for the attack, the deadliest on the army since 15 weeks of battles last year with al-Qaida-inspired Islamist gunmen from Fatah al-Islam in and around Nahr al-Bared camp for Palestinian refugees in Tripoli. The fighting left 400 people dead, including 168 soldiers, and flattened the camp.

Speculations varied on who could be responsible for Wednesday's attack, in which the bomb was made up of 20 kilograms (44 pounds) of explosives.

Some commentators suggested that Fatah al-Islam, defeated by the army last September but not completely eliminated, may have been taking its revenge.

Others hypothesized that the bombing may have been related to the recent sectarian clashes between Sunni supporters of Prime Minister Fouad Siniora in the Bab al-Tebbaneh neighborhood and their pro-Syrian Alawite rivals in Jabal Mohsen district.

Fierce battles between the two communities in June and July left 23 people killed, but sporadic skirmishes have continued, the latest of which was Tuesday night when Bab al-Tebbaneh, just one mile from the site of Wednesday's attack, was hit by a hand grenade and two rockets.

The tension between the Sunnis and Alawites there dates back to Lebanon's 1975-1990 civil war. The Alawite faith, an offshoot of Shiite Islam of which Syria's president is a follower, straddles across to the Syrian territory.

Lebanese commentators argued that the location and timing of the attack may have been aimed at spoiling the growing rapprochement with Syria and disrupting Suleiman's important visit to Damascus to begin later in the day.

Lebanese Information Minister Tareq Mitri said it was too early to speculate on who was behind the Tripoli attack.

"The investigation has begun and there are many interpretations, political interpretations," Mitri told reporters in Beirut. "Once again, they want our country to be an arena for settling scores and battling for influence."

Mitri, like other Lebanese leaders, would not conjecture who "they" could be, amid skepticism that the authorities would succeed in finding the perpetrators after a wave of assassinations of mostly anti-Syrian politicians and public figures have remained unsolved since the murder of former Prime Minister Rafik Hariri in February 2005.

A pro-Western coalition of Lebanon's political leaders has blamed the Syrian regime for the assassination of Hariri and subsequent figures, which Damascus has consistently denied.

It was Hariri's killing in a massive explosion in Beirut that sparked domestic and international pressure on Syria, Lebanon's former powerbroker, to withdraw its troops from Lebanon in April 2005 after an almost 30-year presence.

Suleiman's two-day visit to Damascus, the first by a Lebanese president since the Syrian withdrawal, is aimed at improving ties between the neighboring countries, namely to establish diplomatic ties for the first time since their independence from French colonialism more than 60 years ago.

Assad said in June that Damascus was ready to open an embassy in Beirut and exchange ambassadors once the Lebanese unity government was formed, effectively recognizing Lebanon's independent sovereignty.

The Lebanese president's visit comes just one day after parliament finally gave a vote of confidence to the new coalition government grouping an anti-Syrian parliamentary majority and veto-wielding members of the Damascus-backed Hezbollah-led opposition.

Parliament endorsed the 30-member cabinet after a week of heated debates among rival lawmakers on disputed issues, namely Hezbollah's anti-Israeli weapons that it wants to keep.

Suleiman and Assad will also discuss thorny questions, such as demarcating their borders, their prisoners in each other's countries, the presence of militant pro-Syrian Palestinian factions in Lebanon, and they will review longstanding accords.