The top Republican on the Senate Armed Services Committee is worried about a growing number of fellow Republicans that are open to cutting the Pentagon's budget.

Sen. John McCain (R-AZ) told a foreign policy forum Monday that he was concerned about "the rise of protectionism and isolationism in the Republican Party."

"I think there are going to be some tensions within our party," McCain said.

The lawmaker told the group that he he worried "a lot" about the possibility that Republican support for the war in Afghanistan could fray.

McCain singled out Sen.-elect Rand Paul (R-KY) who has said the GOP must consider military spending cuts.

"Bottom line is, you have to look at everything across the board," Paul said during an appearance on CBS' Face the Nation.

"Everything has to be on the table," he told PBS. "We have to do this intelligently."

"I admire his victory," McCain said. "But... already he has talked about withdrawals [and] cuts in defense, et cetera, And a number of [other Republicans] are."

McCain is right to worry because Paul isn't the only Republican eyeing defense spending.

Sen. Johnny Isakson (R-GA) told Fox 5 Atlanta that reducing the deficit "begins with the Department of Defense and goes all the way through."

In a November op-ed, Sen. Tom Coburn (R-OK) declared, "Republicans also should resist pressure to take all defense spending cuts off the table."

Sen.-elect Mark Kirk (R-IL) said in a debate that he backed "across the board reductions" in the Pentagon's budget.

"There's no doubt that this new group of Republicans have come in with a commitment to take a meat ax to spending," McCain said. He underlined it would be hard to declare military outlays "sacrosanct" in such an atmosphere.

With a report from AFP.