A U.N.-brokered peace deal for Syria appeared in jeopardy Sunday, as the country's main rebel group refused the government's demand for “written guarantees” it would stop fighting before any troop pullout.

The commander for the rebel Free Syrian Army, Riad al-Asaad, said Sunday that his group was ready to honor the truce set for April 10, but would never surrender its weapons.

Earlier, the Syrian government said it wanted iron-clad assurances that insurgents would stop fighting before it implements a troop withdrawal from cities.

Foreign Ministry spokesman Jihad Makdessi said Syria would not allow a repeat of what happened during the Arab League's observer mission in January, when he said the government pulled its forces back only to see rebels rearm and take control of “entire neighborhoods.”

Meanwhile, U.N.-Arab League envoy Kofi Annan said in a statement that he was “shocked” by recent reports of “a surge in violence and atrocities in several towns and villages.”

His comments come a day after Syria's main opposition group reported that nearly 130 people — mostly civilians — were killed across the country. Also, activists blamed Syrian troops Sunday for continuing assaults in the north and center of the country, killing and wounding dozens of people.

U.N. Secretary-General Ban Ki-moon has sharply criticized the Assad government for its continued assault on civilians and said the cease-fire deadline “is not an excuse for continued killing.”

U.N. officials say more than 9,000 people have been killed in Syria since the uprising began 13 months ago.