BERLIN  Chancellor Angela Merkel said Monday that Germany would support much tougher sanctions against Iran in a bid to halt its nuclear ambitions.

“We will work for more sanctions,” she said at a joint news conference with the Israeli prime minister, Benjamin Netanyahu. “We always called for transparency and cooperation with Iran, but unfortunately Iran has not responded.”

Germany is one of the six powers that have been working to curb Iran’s nuclear program, which the West says is aimed at producing nuclear weapons. Those nations met Saturday and agreed that Iran’s response to their latest proposal was inadequate, but failed to agree on new sanctions.

Mrs. Merkel’s comments, after a summit meeting with Mr. Netanyahu and a historic joint cabinet meeting here between the German and Israeli governments, were also aimed at allaying Israel’s fears that it could become a target if Iran obtained nuclear weapons.