*Editor's note: This story has been updated throughout.
U.S. Sen. John Cornyn, R-Texas, said Friday he is concerned about a proposal floated by President Donald Trump's administration as a way of paying for a wall along the U.S.-Mexico border.
On Thursday, Trump appeared to endorse a proposal to put a 20 percent tax on all imported Mexican goods, but a spokesman later said it was just one option available to fund the wall.
"I have concerns about it," Cornyn, the No. 2 Republican in the Senate, told reporters after a speech in Austin. "I want to make sure we know what the consequences are going to be and exactly how this would work."
Asked how serious Trump is about the tax proposal, Cornyn replied, "We’re getting mixed signals from the administration on it. I think we need to pin that down."
Cornyn specifically expressed concern about the tax's potential impact on the United States' imports of heavy crude oil.
"Those would all be subject to the tax," Cornyn said. "One refiner told me that they thought that that might increase the cost of gasoline by 30 cents."
Cornyn hinted Thursday he was not entirely onboard with the tax, tweeting that there are "many unanswered questions about proposed 'border adjustment' tax."
House Speaker Joe Straus, R-San Antonio, appeared to also weigh in on the idea Friday, noting that the United States and Mexico "have a productive economic partnership that is especially good for Texas and San Antonio."
"I hope the new administration will consider the value of this relationship and its economic impact, from job creation to prices at the grocery store, as it contemplates trade policy going forward," Straus wrote on Facebook.