Retiring Sen. Tom Harkin expressed strong moral opposition to the Keystone XL pipeline hours ahead of a scheduled Senate vote to fast-track its approval.

“Every dollar that we spend on fossil fuel development and use is another dollar we spent digging the graves of our grandchildren,” the Iowa Democrat told reporters in the Capitol on Tuesday afternoon. “And I’m not going to be a part of it anymore. I’m through. That’s just how strongly I feel.”

“I know we can’t solve it overnight, but we have to be on a steep glide-path in getting rid of fossil fuels as a source of energy,” he said.

The legislation, which has already passed the House, needs 60 votes to pass the Senate on Tuesday and head to President Barack Obama’s desk for his signature. Although it’s not clear there are 60 Senate votes to pass the bill, Obama has signaled he may veto it if it passes Congress.

Harkin, of course, intends to vote “no.”