The head of U.S. Central Command still believes there is chance to help the civilians under siege in Aleppo, but military action is not the best option.

“The most viable option we have is diplomacy,” Army General Joseph Votel said today.

"There certainly are military things that we can do, we can help facilitate the humanitarian aid, we could potentially target those who would go after that," he said. "There certainly has been discussion of safe zones and other things like that that could have a military component to ensuring those."

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But Votel said that initiating a military action like a safe zone or no-fly zone would not be a simple decision.

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"Those are all things that certainly could be considered but there are many factors I think that go into the decisions to do those things, particularly the decision that you have to be prepared to use force if people do oppose those things," he said. "And so I think those are very weighty decisions that have to be taken into careful consideration."

Syrians at the site of airstrikes in the rebel-held neighborhood of Bustan Al Qasr in Aleppo, Syria, 28 April 2016. ZOUHIR AL SHIMALE / EPA

Thousands of Syrian regime soldiers, Iranian military troops, and Hezbollah fighters have been massing around Aleppo for weeks, often pushing in and striking inside the city.

Asked whether those ground forces are a sign that it’s too late for a no-fly zone, General Votel tried to sound optimistic that it isn’t too late for the civilians in Aleppo.

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"I am generally a more hopeful person so I always think there is an opportunity. We should always look for opportunities where we can diplomatically or otherwise help change the situation for the better for people on the ground," he said.

"We always have to stay engaged, we always have to be looking for where there are opportunities to step in and do things that support our value and help people on the ground."