Federal agents, taking a step that could endanger delicate peace talks between the government and Chiapas rebels, announced Monday they had arrested a former guerrilla leader on a weapons charge.

Analysts said the arrest Saturday of Fernando Yanez Munoz, one of the rebel movement’s founders, who was known as Comandante German, could reverse gains made in talks to end the 22-month uprising.

They said the rebel Zapatista National Liberation Army could well consider the arrest a violation of an agreement to suspend arrest warrants for the rebel leaders as long as peace talks were under way.

“This is practically a declaration of war, and in reality implies a breaking of the truce,” said Juan Fernando Reyes Pelaez, a researcher for the Center for Historical Research into Armed Movements.