The U.S. Senate moved on Tuesday toward ramming through approval of President Donald Trump's Supreme Court nominee this week, as its top Republican said he had the votes to wipe away Democratic roadblocks but vowed to preserve the minority party's ability to hold up legislation.

Majority Leader Mitch McConnell plans to change the Senate's long-standing rules in order to eliminate the ability to use a procedural hurdle called a filibuster against Supreme Court nominees like Trump's pick, Neil Gorsuch, if a Democratic filibuster succeeds as expected in blocking a confirmation vote.

Senate confirmation of Gorsuch, 49, to the lifetime post would restore the court's conservative majority and enable Trump to leave a lasting imprint on America's highest judicial body even as he regularly criticizes the federal judiciary.

McConnell said he had the necessary votes to approve the rule change with a simple majority vote, expected on Thursday. Republicans control the Senate 52-48. The rule change has been dubbed the "nuclear option," and Trump has encouraged McConnell to "go nuclear."

Such a step would threaten to further erode trust between the parties in Congress.

"There's a reason they call it the nuclear option, and that is because there's fallout. And this fallout will be dangerously and perhaps disastrously radioactive for the Senate for years to come," Democratic Senator Richard Blumenthal told reporters.

Republicans were so confident they could use their muscle to pass the rule change that Senate Judiciary Committee Chairman Chuck Grassley said flatly that Gorsuch "will be on the Supreme Court Friday night."

Amid a fierce debate over both Gorsuch and the Senate's rules, McConnell tried to tamp down any speculation that Republicans would stage a monumental power grab by ending the filibuster for legislation.

McConnell said that as long as he was the Senate's majority leader, he would never remove the ability to mount a filibuster against legislation, as opposed to presidential appointments. McConnell fought against many of former Democratic President Barack Obama's legislative initiatives when Republicans were the minority party in the Senate.

"There's not a single senator in the (Republican) majority who thinks we ought to change the legislative filibuster, not one," McConnell told reporters.

The move to change venerable Senate rules reflects an intensifying of the already-toxic partisanship in Washington since Trump took office in January.

McConnell's promise to keep the ability to filibuster legislation could make it more difficult for Republicans to get key parts of Trump's legislative agenda through the Senate, considering the expected strong Democratic opposition.