Syria's opposition on Wednesday denounced what it called "threats" by the head of Hezbollah, and warned against any intervention by the Lebanese Shiite group or by Iran in the Syrian conflict.
The speech was also criticised by Lebanese opposition leader Saad Hariri, who accused Hezbollah of "leading Lebanon to ruin" by intervening in Syria.
"The Syrians and the Lebanese hoped... that the Hezbollah leadership would stop their attacks on Homs and Damascus and take into account the gravity of the situation in the region," the Syrian National Coalition said in a statement.
"But they heard nothing but threats... and warnings against setting the region on fire and an admission of their interference in Syrian affairs," the key opposition movement said.
On Tuesday, Hezbollah chief Hassan Nasrallah acknowledged that members of the group are fighting inside Syria and suggested Iran and other states could intervene to support the Damascus regime against rebels.
President Bashar al-Assad has "true friends in the region who will not allow Syria to fall into the hands of the United States, Israel and 'takfiri' groups," he said of Sunni Muslim groups battling the regime.
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"If the situation gets more dangerous, states, resistance movements and other forces will be obliged to intervene effectively in the confrontation on the ground," he added.
"You will not be able to bring down the regime militarily," Nasrallah told Syria's rebel forces. "The battle is still long."
The Syrian opposition has long accused Hezbollah of dispatching fighters to fight alongside government forces, including in Qusayr in central Homs province and at the Sayyeda Zeinab shrine near Damascus.
The Coalition called on the Lebanese government "to immediately put an end to Hezbollah military operations in the regions close to the Syrian border."
Hariri slammed Nasrallah in a statement, saying he "gave himself the right to expand Hezbollah's operations from southern Lebanon to Qusayr and Sayyeda Zeinab in Syria."
"Nasrallah is telling us that the (Lebanese) state... will forever be a hostage in the hands of Hezbollah," he added, accusing the group of "leading Lebanon to ruin."
He called on Lebanon's citizens, "whatever their positions, to assume their historic responsibilities by standing against this project and using all democratic methods to reject it."