"Iran is the most irresponsible force in the world," Netanyahu told reporters during a visit to Cyprus. "I hope the sanctions will have an effect, but so far they have not. We are dealing with a regime that violates every resolution and has no respect for international standards.
"Iran's race towards nuclear weapons should concern the U.S. and every other country. Nuclear arms in the hands of such a regime is a cause for great concern to the U.S. and Israel."
Netanyahu's comments, reported by Ynetnews.com, come a day after Iran claimed it has put its first domestically made nuclear fuel rods into a nuclear reactor.
Iran has said its nuclear program is for peaceful purposes, but Western countries have tightened sanctions amid concerns the country is working to develop nuclear weapons.
Netanyahu was in Cyprus for a one-day visit designed to strengthen cooperation between Jerusalem and Nicosia in energy, agriculture, health and maritime research.
He and Cypriot President Dimitris Christofias signed an agreement that will authorize each country's aircraft to enter the other country's airspace if there is a disaster.