Despite substantial gains this week by the Islamic State group in Iraq and Syria, the White House made clear that President Barack Obama has no plans to send combat troops into the region.

"The president is not going to be in a position where he is going to consider a large-scale military deployment," White House spokesman Josh Earnest said Thursday. "And for those who are calling on a change in strategy, I would encourage them to be specific."

"I don't think that they will find either a lot of support on the part of the American people for a large-scale deployment of military resources to essentially re-invade Iraq or invade Syria," Earnest added.

This week, the Islamic State group expanded its control over key cities in the area - Ramadi in Iraq and Palmyra in Syria - prompting some lawmakers to call for a clear plan of action.

"With new gains made by ISIL in Ramadi, we know that hope is not a strategy," said House Speaker John Boehner, R-Ohio, ABC News reported. "The president's plan isn't working. It's time for him to come up with a real, overarching strategy to defeat the ongoing terrorist threat."

In an interview with The Atlantic, President Obama referred to the Islamic State group's gains as a "tactical setback," but said, "I don't think we're losing."

Earnest defended the president's decision to call the fall of both cities a setback. When asked by a reporter whether he thought it was more than a mere setback, Earnest responded, "No, I don't think it is. I think it is a setback." Earnest said Obama noted "that this military conflict, like other military conflicts, would be characterized by days of progress and by periods of setback."

Even with the loss of territory, Earnest said the administration's strategy hasn't changed, which partially consists of thousands of U.S.-led coalition airstrikes in support of Iraqi forces on the ground. "We are in the degrade portion of this operation," Earnest said, which also includes "things like shutting down financing of their operations, countering their efforts to recruit people from around the globe and stemming the flow of foreign fighters to this region of the world."

"But overall," Earnest added, "what we're talking about here is a strategy that builds up the capacity of local fighters to fight for their own country. And that is a significant departure from the strategy that's advocated by many Republicans, which is the large-scale American military deployment in Iraq and in Syria that didn't work so well the last time we tried it."

The U.S. cannot indefinitely fight wars for other countries, Earnest said. "No matter how difficult this challenge is, this is not something the United States is going to do for the Iraqi government, and we're certainly not going to do it for Syrian government. There's going to be the responsibility of the Iraqi people and the Syrian people to take the fight on the ground, for their country, against ISIL."

Earnest said the administration is constantly refining its strategy, but wouldn't comment on what it would take to draw U.S. ground forces into the fight.

"The broad outlines of this strategy that involve building up the capacity of local fighters by training and equipping them, by offering them military advice where necessary to take the fight to ISIL in their own country, and backing them with military airpower, that is the broad outlines of our military strategy, and that is consistent with our national security interests," Earnest said. "It also, in the mind of the President, is the best way for us to succeed over the long term."