A key Republican senator dressed down the Obama administration's war planners on Wednesday, describing as "embarrassing" their admission that the Pentagon hasn't implemented a no-fly zone in Syria out of fear of confronting provocations from the Syrian and Russian militaries.

In testimony before the Senate Armed Services Committee, Air Force Gen. Paul Selva confirmed the military has the ability to implement a designated area in Syria that it could protect with air power and use as a safe zone for refugees fleeing their homes. But, he said, political and policy realities are restricting America's ability to follow through.

"If we're asking the question, 'Can we do it?' the answer is 'yes.''" said Selva, vice chairman of the Joint Chiefs of Staff. "Are we willing to engage the potential of a direct conflict with the Syrian integrated air defense system or Syrian forces or, by corollary, a confrontation with the Russians, should they choose to contest the no-fly zone?"

Those are the questions that have been asked, Selva said, and answered.

"We have not recommended it because the political situation on the ground and the potential for miscalculation and loss of American life in the air in an attempt to defend the no-fly zone don't warrant the no-fly zone."

The response by Selva, the second-highest military officer in the country and chief adviser to President Barack Obama, visibly angered some members of the committee, particularly its chairman, Sen. John McCain.

"General, I must say, that's one of the most embarrassing statements I've heard from a uniformed military officer," said the Arizona Republican, who has been one of the most vocal proponents of a no-fly zone since the beginning of the Syrian civil war. "That we are worried about Syria's and Russia's reaction to saving the lives of thousands and thousands of Syrians who are being barrel bombed and massacred. So far, 240,000 of them."

"Remarkable performance," McCain said sarcastically.

The heated exchange represents the core of criticisms against the Obama administration's handling of the civil war, which began in 2011, and the subsequent war against the Islamic State group, which capitalized on regional unrest last year to establish its so-called caliphate now spanning the Syria-Iraq border.

The number of people expelled by the fighting reached a critical mass during the summer and sparked a refugee crisis as millions fled Syria and headed northward toward Europe. The subsequent political response bolstered calls by Republicans for a no-fly zone – a move that has been supported by some Democrats, including presidential front-runner and former Obama Secretary of State Hillary Clinton, who has increasingly distanced herself from the president's handling of the crisis.

The potency of the extremist group – also known a ISIS, ISIL or Daesh – has garnered increased international attention for providing planning or inspiration for attacks in Paris, San Bernardino and elsewhere.

Opponents, including McCain, believe the U.S. must focus on a decisive military defeat of the extremist network before it can repair regional societies to ensure another group cannot rise in its wake, as the Islamic State group did after the effective destruction of al-Qaida in Iraq. The White House, however, is focused on avoiding playing into the Islamic State group's narrative that it is preparing for an apocalyptic battle between the faithful and Western invaders, for which it has so effectively recruited disaffected young people.

U.S. Secretary of Defense Ash Carter shakes hands with Sen. John McCain (R, Ariz.), Senate Armed Services Committee Chairman, as he arrives to testify during a hearing Wednesday on Capitol Hill.

Saul Loeb/AFP/Getty Images

Selva reaffirmed the basic structure of the administration's approach during pointed questioning by Sen. Claire McCaskill on Wednesday. The Missouri Democrat blasted fellow committee member Ted Cruz, R-Texas, for his absence at the hearing, and for his recent rhetoric that if he succeeds in his campaign for president he would "carpet-bomb" areas of the Middle East to defeat the Islamic State group.

"We have to be careful about how we prosecute a campaign that appears to be an indiscriminate attempt to attack ISIL and the population around," Selva said.

However, Obama appears to have loosened up some authorities on waging the war against the Islamic State group in the wake of criticisms from top officials – including all of his former secretaries of defense – that the White House micromanages important details of the campaign.

Defense Secretary Ash Carter, who testified alongside Selva, said the general commanding the new position to oversee the anti-Islamic State group campaign has the authority "in many cases" to direct a new commando unit to conduct raids within Iraq or Syria without first getting clearance from Washington.

"There will and has to be a certain amount of delegation authority here," Carter said, adding that intelligence gleaned from such raids frequently yield another target that would need to be assaulted shortly after.

The entirety of the U.S. shift in its war against the Islamic State group means more Americans will be on the ground, waging combat and in harm's way.

Carter also indicated Wednesday that the special operations forces who help guide in air strikes – known as Joint Terminal Air Controllers – have moved outside of the headquarters to which they were previously restricted and are now accompanying local forces on the ground to improve the precision of warplanes' strikes.

"And, by the way, [we're employing] other skills, intelligence skills and other skills that allow us to leverage local forces and make it much more powerful by bringing in the full weight of America's might behind it," he said.