WASHINGTON -- Outraged at the beheading of U.S. journalists by "barbaric" terrorists, Reps. Steve Israel and Peter King said President Barack Obama must do more to fight the menace of the Islamic State group.

As Obama Wednesday defined the U.S. goal -- to "degrade and destroy ISIS so that it is no longer a threat" -- he won some Democratic support and a lot of Republican criticism from House members and candidates from Long Island.

Israel, a Huntington resident and member of the House Democratic leadership, complained Obama could have acted sooner to curb the Islamic State -- also known as ISIS -- by arming moderate rebels in Syria.

Israel also urged Obama to extend U.S. military action against Islamic State fighters in Iraq to those on the Syrian side of the border, which Obama said he's not ready to do.

"We've got to fight this," Israel said. "This is a clash of civilizations and it's a clash of centuries . . . between the 21st century and the 14th century," he said.

Israel said when Obama attends a NATO summit in Wales Thursday, he should propose a new NATO to combat terror.

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"We need a new military coalition that operates like NATO, but with a counterterrorism capability aimed at stopping" such groups, he said.

King, a Seaford Republican who chairs the House counterterrorism subcommittee, complained that Obama continues to project weak leadership.

"We need something firm and declarative, and not a mixed message," King said. "I supported the statement he gave, but then he qualified it."

When pressed on his "degrade and destroy vow," Obama said he wants to ensure ISIS is "not an ongoing threat to the region" and "degraded to the point it is no longer the kind of factor that we've seen the last few months."

Nassau community activist Patricia Maher, the Democrat running against King, backed Obama's cautious approach.

"Jumping into the fire too quick will only lose more American lives right here at home," she said.