Washington (CNN) President Donald Trump suggested Wednesday that a 25 cent increase in gas and diesel taxes would be needed to help pay for the administration's new infrastructure plan, according to Democratic Sen. Tom Carper.

In a bipartisan meeting with lawmakers at the White House, Trump noted that the federal gas tax hasn't been raised since 1993, said Carper, the top Democrat on the Environment and Public Works Committee.

"He said that he knew it was a difficult thing for legislators to support and said that he would support the leadership to do that and provide the political cover to do that," Delaware's Carper told CNN in an interview. "And he came back to that theme again and again and again."

Transportation Secretary Elaine Chao did not rule out a gas tax Tuesday when she spoke to reporters at the White House, but she described it as "not ideal."

"The President has not declared anything out of bounds, so everything is on the table. The gas tax, like many of the other pay-fors that are being discussed, is not ideal," she said. "There are pros and cons. The gas tax has adverse impact, a very regressive impact, on the most vulnerable within our society; those who depend on jobs, who are hourly workers. So these are tough decisions, which is why, once again, we need to start the dialogue with the Congress, and so that we can address these issues on this very important point."

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