What should the US do after Russia exits Syria

After Russia has promised to withdraw most of its forces from Syria, it remains unclear why President Vladmir Putin has made such a move.

Wesley Clark, a retired four-star general and former NATO supreme allied commander, told CNBC's "Power Lunch" on Tuesday that there are several possible reasons why Putin may have promised a withdrawal.

"One reason to do it is because, frankly, Russia's economy is short on funds and maybe wants the defense money to go somewhere else," Clark suggested. "Another reason to do it is maybe this pleases the Europeans and he's making efforts to get sanctions relieved."

Clark also said that Putin may have use for these forces elsewhere.

"Maybe there's a role for these Russian forces returning to reinforce Putin's hand in Ukraine," Clark added, "We don't know all his motives at this point."

Clark said that while Russia has pulled out of Syria, there is still plenty of uncertainty in the region. He pointed to the fact that Turkey is struggling to balance the demands of an immigration crisis while dealing with domestic terrorism.

There's also the Iran agreement and lingering concerns about counterproliferation efforts. To help resolve these issues, Clark said that the United States will have to walk a fine line when working with local authorities.

"We have to work with [President of Turkey, Tayyip Erdogan]. We can't run Turkish democracy for them. We tried that in Iraq," Clark said.

"The United States, we have to concentrate on our own economic development," Clark said. "We've got a full agenda of things to work on and of course we should try to encourage all of our allies to adopt the kind of democratic values and human rights that we believe in, but you have to keep everything in balance."

"We've got to find ways to finesse it, to bring the region together to end the conflict if we can and we certainly don't want to put a bunch of U.S. troops in there in another conflict situation."