The Trump administration needs to finalize regulations overhauling a visa program that provides green cards to foreign investors, Sens. Charles Grassley and Patrick Leahy said.

“We believe they will generate increased capital investment for the United States economy, and will help ensure that some portion of that capital is actually invested in rural and underserved areas, as Congress intended,” the two lawmakers said in a March 11 letter to the Homeland Security Department and White House Office of Management and Budget.

Grassley (R-Iowa) and Leahy (D-Vt.) have been the chief critics of the EB-5 immigrant investor program for years, even calling for its abolition when congressional talks on the program’s overhaul broke down. The program provides green cards to foreign nationals who invest at least $500,000 in U.S. commercial enterprises that create at least 10 jobs.

The two senators say current program rules contain loopholes that enable fraud, as evidenced by a series of lawsuits brought by the Securities and Exchange Commission. They also believe that the structure of the EB-5 program doesn’t properly channel investments into areas of the U.S. in greatest need of funding.

The DHS unveiled a proposal to overhaul the program in the final days of the Obama administration in January 2017. Finalized regulations were sent to the OMB for review Feb. 22.

Grassley, Leahy, and former Rep. Bob Goodlatte (R-Va.) previously asked for the regulations to be finalized in April 2018 after their attempt at a legislative solution fell through.

Stakeholders primarily are concerned with the potential increase in minimum investment amounts under the regulations, which they say would drive down demand for the visas. Under the proposal, the minimum would jump from $500,000 to $1.35 million.

Representatives for the DHS and OMB weren’t immediately available for comment.