The United States says Lebanon's Hezbollah militia is stepping up support for the Syrian government and has become part of President Bashar Assad's "killing machine."

U.S. Ambassador Susan Rice told the U.N. Security Council's monthly meeting on the Mideast on Monday that Hezbollah leaders are also continuing to plot new measures with Iran "to prop up a murderous and desperate dictator" in Syria.

She said the United States is encouraging the international community "to counter Hezbollah's terrorist activity and do more to expose Hezbollah's deepening involvement in Assad's war."

Israel's U.N. Ambassador Ron Prosor says that in such Syrian cities like Homs, Hama and Damascus, Hezbollah's militia is "butchering their Arab brothers and sisters."

Hezbollah fought a war against Israel in 2006 and is a major political and military force in Lebanon.