BOGOTA, Colombia — Guerrillas in Colombia have begun to lay down their weapons as part of last year’s historic peace agreement, injecting a much-needed dose of optimism after weeks of feuding over the slow pace of the accord’s implementation.

The United Nations on Thursday said that it had collected some 2,300 weapons that were handed over a day earlier by guerrillas belonging to the Revolutionary Armed Forces of Colombia. That represents a little more than a third of the FARC’s declared arsenal of weapons, the U.N. mission in Colombia said.

“This is a major development that bears witness to the parties’ will to respond to the hope generated in Colombia and the international community by the peace agreement signed last November,” the U.N. said.

Almost since the accord was signed, the FARC and government have been squabbling over what rebels complain is foot-dragging by the government in passing implementing legislation, freeing jailed rebels amnestied under the accord and investigating murders of leftist activists in areas they once dominated.

Amid the bickering, the FARC missed the original May 31 deadline to conclude the disarmament process. Under a deal worked out by the two sides last week the remainder of its weapons must be handed over by June 20.

“We will never use violence again. That’s what we promised and we will deliver,” the FARC’s top commander Rodrigo Londono told rank and file guerrillas Wednesday at a camp in northeastern Colombia, one of 26 nationwide where 7,000 fighters are making their transition back to civilian life.

His comments were broadcast in a FARC-provided video. Neither the FARC nor the U.N. would provide images of the actual handover, irking some conservative opponents of the peace accord who suspect — without any evidence — that the rebels are withholding their heaviest artillery and only turning over light weapons of limited battlefield

The weapons are being stored by the U.N. at containers.