WASHINGTON — Sending thousands more American troops into Iraq or Syria in a bid to accelerate the defeat of the Islamic State group would push U.S. allies to the exits, create more anti-U.S. resistance and give up the U.S. military’s key advantages, Defense Secretary Ash Carter said in an Associated Press interview.

Speaking from his Pentagon office Wednesday, Carter said he favors looking for ways to speed up the counter-IS campaign, which administration critics, including Donald Trump, have called slow-footed and overly cautious.

But he outlined numerous reasons why he believes strongly in the current approach of letting local Iraqi and Syrian forces set the pace.

“If we were to take over the war in Iraq and Syria entirely ourselves, first of all, in the near term it would be entirely by ourselves, because there is no one else volunteering to do that,” he said. “We could get past that. But secondly, we would risk turning people who are currently inclined to resist ISIL” or to join ranks with the coalition, “potentially into resisting us.”

Taking over the war also would amount to “fighting on the enemy’s terms, which is infantry fighting in towns in a foreign country,” he said. While U.S. troops can do that, it would not leverage the U.S. military’s biggest strengths, which are special operation forces, mobility, air power and intelligence-gathering technologies — “exquisite capabilities that no one else has,” he said — to enable local troops to do the fighting and own the outcome.

So while he believes faster is better, “It’s important that it be done in a way that victory sticks.” That was a reference to avoiding a repeat of the disastrous events of 2014, when Islamic State militants swept into western and northern Iraq from Syria and grabbed control of large swaths of territory as the Iraqi army collapsed. The Obama administration was caught by surprise at the hollowness of the Iraqi army, weakened by political and ethnic strife.

The AP interview was Carter’s last as defense secretary. His designated successor, retired Marine Gen. James Mattis, is expected to win easy Senate confirmation shortly after Trump is inaugurated.