When asked if he supports the arms sales outside of regular congressional oversight, Shanahan replied: "My preference is always to follow the process."
Pressed on whether that means he does not support the administration's emergency provision, which was announced in May, Shanahan attempted to clarify.
"No, no, no, my comment is it's always best to support the process. And use the process," he said.
Shanahan did not expand on or offer any additional explanation regarding his comments but an aide to the acting defense secretary later told CNN that he likes the regular process for matters as a rule, but once the decision was made by the administration, he supported it.
In May, Secretary of State Mike Pompeo formally told lawmakers of the administration's plans to declare an emergency as a way to bypass Congress on $8.1 billion worth of foreign arms sales -- primarily to Saudi Arabia and the UAE.
"Our posture regarding Iran remains focused on assuring our partners of our commitment to enhancing their defense capabilities. This action is not intended to be an escalatory military step; instead, it is a loud and clear message to Iran that we stand by our regional partners," Cooper will tell lawmakers in his opening testimony Wednesday.
But the emergency declaration has drawn bipartisan condemnation from members of the House and Senate. Some say the administration is attempting to use a legal loophole.
"President Trump is only using this loophole because he knows Congress would disapprove of this sale," Sen. Chris Murphy, a Connecticut Democrat, said in a statement after the announcement was made in May. "There is no new 'emergency' reason to sell bombs to the Saudis to drop in Yemen, and doing so only perpetuates the humanitarian crisis there. This sets an incredibly dangerous precedent that future presidents can use to sell weapons without a check from Congress."