Turkey and Russia brokered the ceasefire deal last Thursday, and it has mostly held since then.
The peace talks are due to be held in Astana, Kazakhstan.
"The regime and its allies have continued firing and committed many and large violations," the statement issued on Monday said.
"As these violations are continuing, the rebel factions announce... the freezing of all discussion linked to the Astana negotiations," it said.
The groups highlighted fighting in the rebel-held region of Wadi Barada, north-west of Damascus, which they say has been subjected to almost-daily bombing raids and bombardment by Syrian forces and their Hezbollah allies.
The area does not fall under the ceasefire agreement, given the presence of Jabhat Fateh al-Sham (JFS), a jihadist group which was excluded from the deal.
Wadi Barada contains a major spring, which supplies water to millions of residents in the capital. The government has accused the rebels of polluting it with diesel, which they deny.