The Republican leader said Monday that he intends to allow for an open amendment process to the trade legislation, adding that blocking movement on the bill "would be a big mistake." 
"[There's been] some talk about preventing the Senate from even debating the bill," he said. "I would tell you... I think that would be a big mistake." 
The Senate is scheduled to take an initial procedural vote Tuesday, on ending debate on a motion to proceed to the bill.
The legislation, which would block Congress from amending a trade pact the administration is negotiating with 11 Pacific Rim countries, is a rare area of agreement between McConnell and the Obama administration. 
But the vote is pitting the administration against Reid, who has pledged to block the trade bill until senators agree to a way forward on highway and surveillance bills, both of which face end-of-the-month deadlines. 
The Nevada Democrat said Monday that he's "disturbed and distressed" by McConnell's priorities. 
"With only a few days before the Memorial Day recess, I'm disturbed and distressed by Republicans' priorities," he said. "For example, the majority leader knows that the reauthorization for the federal highway program expires this month."
Reid is part of a contingent of Senate Democrats who remain staunchly opposed to the trade legislation, worried that it could undercut workers in the U.S. 
Fourteen Senate Democrats on Monday urged Obama to bolster labor standards before the Asia-Pacific trade deal goes into effect. 
Despite the Democratic skepticism, it's unclear if Reid will be able to garner enough support to carry out his threat to block the legislation. 
But the Kentucky Republican said on Monday that "it's incredibly important for Americans that we pass this bill." Without it, he said, "foreign countries will be able to discriminate against American products."