Foreign-based Syrian opposition National Coalition said Friday that it would not attend next month's Friends of Syria meeting in Rome.
The group, formed in Doha in November, said the planned boycott was in protest against a lack of international condemnation of the "crimes committed against the Syrian people."
The international community "amounts to participating in two years of killings" by keeping silent on "the crimes committed every day against our people," it said in a statement.
Due to the "this shameful international position," the coalition has also decided to quit the scheduled talks in Russia and the United States, added the statement.
UN human rights chief Navi Pillay has placed the death toll from Syria's 23-month-old turmoil at nearly 70,000.