The group had earlier indicated that it was going but also said it required confidence-building measures, including humanitarian corridors to besieged rebel areas and the release of political prisoners.
Al-Jarba reiterated the coalition's stance that it sees the conference as leading to a transitional government. The Syrian opposition and its Western supporters insist that Assad cannot be part of such a government.
In a jab at Britain and France, the Foreign Ministry said that if Paris and London "insist on holding fast to these illusions" that there is no place for Assad in a transitional period, then "there is no need for them to attend Geneva 2."
"Our people will not allow anyone to steal their right to decide their future and leadership and the main goal of the Geneva conference is to fulfill the interests of the Syrian people alone, and not those who shed their blood," the statement said.
The continued bloodletting is but one of huge hurdles that remain ahead of talks. The full list of participants also has not been decided.
Al-Jarba said his group rejects Iran's participation in the conference, unless it withdraws forces fighting on Assad's behalf. The Iranian-allied Lebanese Hezbollah group has backed Assad's troops. Iran's Revolutionary Guard has said it has high-level advisers in Syria but denied having fighters there.
In Tehran, the Iranian and Turkish foreign ministers called for a ceasefire as soon as possible, saying that a halt in fighting would enhance chances of peace talks succeeding. The two ministers declined to give details Wednesday at a joint press conference.
In Washington, State Department spokeswoman Jen Psaki said the end goal of the Geneva gathering must be a transitional government.
She rejected the Assad government's reference to this objective as "foreign demands."
"The goal of Geneva has nothing to do with foreign demands," Psaki said. "It has to do with bringing an end to the bloodshed and suffering of the Syrian people."
Previous attempts to bring Syria's government and opposition to the negotiating table have failed. The disputes have centered on who should represent the two sides, whether Iran, Saudi Arabia and other regional powers should be at the table, and above all whether Assad will remain in office.
Syrian officials say Assad will not surrender power and may even run again in elections due in mid-2014.
His government has bolstered its negotiating position with a string of victories over the past month, capturing several rebel-held suburbs on the southern fringe of Damascus and two towns outside the northern city of Aleppo.
On Wednesday, forces loyal to Assad clashed with rebels trying to break a government blockade of opposition-held suburbs east of the capital, the Britain-based Syrian Observatory for Human Rights said. It said at least 17 rebels were killed along with an unknown of pro-government fighters.
Syrian state media had no word on the clashes.
The Observatory said the fighting was focused in the village of Marj in the eastern Ghouta area, and pitted rebels from two al-Qaida-linked groups, Jabhat al-Nusra and the Islamic State in Iraq and the Levant, against government troops and its Shiite allies from the Lebanese Hezbollah group and the Iraqi Abu al-Fadl al-Abbas brigade.
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Negus reported from Cairo. Associated Press writers Bradley Klapper in Washington and Ryan Lucas in Beirut contributed to this report.
