(CNN) -- The Syrian National Coalition, the country's principal opposition group, says it is suspending its participation in the upcoming Friends of Syria conference in Rome "in protest of the shameful international position."
After missiles killed dozens in Aleppo on Friday, the group said on its Facebook page that it "considers the international silence toward the crimes committed every day against our people is, in effect, participation in the ongoing slaughter for the last two years."
Adib Shishakly, representative of the Syrian National Coalition to the Gulf Cooperation Council, told CNN on Friday, "enough is enough. The whole world is not doing anything. We are not going to more conferences. We are not going to Rome. We are not going to Moscow."
He said Scud missiles were used in the Aleppo shelling.
The opposition is tired of international community holding meetings without providing needed assistance, Shishakly said.
Rebels want military aid, including arms and training.
"We want the U.S. to help the people on the ground," said Shishakly, adding other nations must pressure Iran to stop providing ballistic missiles to the Syrian government.
The Friends of Syria is a collection of dozens of countries trying to find a solution to the Syrian crisis.
A senior U.S. official told CNN that the Syrian coalition had not notified the United States of its decision ahead of its announcement.
Regardless, boycotting the Rome meeting next week would be counterproductive to the opposition, the official said.
The meeting will provide the opposition its first opportunity to meet new Secretary of State John Kerry, according to the official. It also will cover streamlining efforts to get aid directly to the group.
The Syrian National Coalition also is not accepting invitations to visit Washington, D.C., and Moscow.
The rebellion against President Bashar al-Assad's government began in earnest in May 2011 as a wave of uprisings spread across the Arab world, including Tunisia, Algeria, Libya and Egypt.
The United Nations recently estimated 70,000 people have died in the fighting in Syria.
The opposition Local Coordination Committees in Syria said 213 people were killed Friday, including 92 in Aleppo. It said 307 demonstrations occurred across the country. CNN could not independently verify those numbers.
CNN's Elise Labott and Amir Ahmed contributed to this report.