Senate Democrats on Wednesday plan to block legislation that would impose more stringent background checks on Syrian refugees, even though the measure had bipartisan support in the House in November.

Senate lawmakers are scheduled on Wednesday to hold a key test vote on the measure, which would boost screening requirements for Syrian and Iraqi refugees seeking to relocate in the United States. Supporters are worried that members of the Islamic State may try to sneak into the United States by posing as refugees.

The measure passed the House in November with 46 Democrats. That was just enough to create a two-thirds majority, which is needed to override a veto from President Obama, although an actual override vote might go differently.

But Senate Democratic leaders say it will never make it to Obama's desk because they'll block it in the upper chamber. Republicans control 54 votes, which is six shy of the 60 needed to bring the bill to the floor for debate.

"Don't worry, it won't get passed," Reid said when asked recently about the legislation.

The Democratic plan will aid Obama, who has promised to veto the legislation if it somehow found its way out of the Senate. Obama administration officials say the legislation's security requirements are not achievable and would prevent the United States from helping the most desperate Syrian and Iraqi refugees who are fleeing war and Islamic State terrorists.

The bill would require FBI and other federal security certification of each new refugee, a requirement that the GOP admits would essentially hit the "pause" button on incoming refugees from the two countries.

The measure quickly and easily passed the House in November and came in response to deadly terrorist attacks in Paris, which were carried out in part by Syrian passport holders posing as refugees.

While Obama is opposed to the bill, he has already signed on to a measure that aims to prevent would-be terrorists from exploiting the visa waiver program. The fiscal 2016 omnibus spending bill signed into law by Obama in December includes a provision that prevents Syrian, Iraqi, Iranian and Sudanese citizens from participating in the visa waiver program. The program currently allows citizens of 36 participating countries to travel to the United States for 90 days with just a passport.

Now, those from the four designated countries must undergo pre-screening before entering the country.

On Tuesday, Senate Majority Leader Mitch McConnell, R-Ky., called on lawmakers from both parties to vote for the legislation.

"It's clear that many Americans are concerned about the administration's ability to properly vet thousands of individuals from Syria and Iraq," McConnell said. "Elected officials in both parties have expressed concerns too, as have administration officials. "That's why many Americans are asking us to take a step back and press 'pause' on the program so we can ensure we have the correct policies and security screenings in place."