Sen. John McCain said Thursday he will block Army Gen. Martin Dempsey's nomination for a second term as chairman of the Joint Chiefs of Staff because he is unsatisfied with Dempsey's response to questions about the potential use of U.S. military power in Syria, The Associated Press reported.

The Arizona Republican senator wanted to hear Dempsey's opinion on which approach would be of greater risk to U.S. national security interests.

The officer responded that he had provided President Barack Obama with military force options, and that he didn't want to influence any decisions with his public opinion. He continued to explain that he'd give the Senate Armed Services Committee details of his recommendations when adequate, AP reported.

After leaving the hearing room, AP reported that McCain told reporters he planned to put a hold on the nomination, blocking any further Senate action until he receives a solid response from Dempsey.

The Syrian civil war has gone on nearly three years, and has killed about 93,000 people, fueling requests for U.S. involvement.

AP reported that Senators including Carl Levin, D-Mich., and McCain have been pressing Obama to take a more forceful approach to defeat Syrian President Assad's forces. While the administration has authorized lethal aid to rebel forces battling Assad's troops, it isn't trying to enforce a no-fly zone in which Syria's combat aircraft would be barred from flying, or otherwise intervene militarily to halt the war, AP said.

During his argument with McCain, Dempsey said "situations can be made worse by the introduction of military force" without clear knowledge on how Syria would manage politically.

Earlier in the year, McCain made a secret visit to the Syrian border in Jordan, where he met with Syrian refugees.

He returned, and expressed refugees' anger about the U.S.'s lack of involvement in the civil war at the time.

McCain leads a bipartisan congressional group pressuring to provide U.S. aid to civilians and Syrian government rebels.