Story highlights "Obviously all of us still carry the scars and trauma of 9/11," he says

"It has to do with me not wanting a situation in which we're suddenly exposed to liabilities," he adds

Washington (CNN) President Barack Obama told CNN's Jake Tapper Wednesday that members of Congress made a "political vote" by voting overwhelmingly to override his veto of a measure that allows families of those killed during the 9/11 terror attacks to sue Saudi Arabia.

"It's an example of why sometimes you have to do what's hard. And, frankly, I wish Congress here had done what's hard," he said in a CNN town hall before a military audience set to air at 9 p.m. ET.

"If you're perceived as voting against 9/11 families right before an election, not surprisingly, that's a hard vote for people to take. But it would have been the right thing to do ... And it was, you know, basically a political vote," Obama said, adding that Gen. Joseph Dunford, chairman of the Joint Chiefs, and Defense Secretary Ash Carter said the legislation was a bad idea.

The override is the first of Obama's presidency -- and was supported by lawmakers from both parties. The Senate approved the override on a 97-1 vote with Minority Leader Harry Reid the lone member to sustain the President's veto. Hours later, the vote in the House was 348-77, with one Democratic member voting "present."

Obama called Congress' move a "mistake."

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