Sen. Marco Rubio, R-Fla., said Monday the “Gang of Eight” comprehensive immigration reform the Senate will debate this month must be changed or it will not pass Congress.

Rubio, in a video response to a constituent letter expressing concerns about the “unintended consequences of a large immigration reform bill,” said that the current legislation, which he supported in a Senate committee last month, will require stronger border security and an improved guest worker program if it is to pass Congress.

“There will have to be improvements,” to prevent future problems with illegal immigration, Rubio said in the video. “If we don’t have that, then we won’t have immigration reform, and I think our country will suffer for it.”

Rubio made the remarks as the Senate prepares to debate S.744, an 800-plus page plan that couples additional border security with instant legalization and a pathway to citizenship for the nation’s 11 million illegal immigrants.

Rubio’s support for the bill has caused him to suffer some backlash among Florida’s Tea Party conservatives who helped propel him to the Senate in 2010. But he was willing to help the bill clear the Senate Judiciary Committee on May 24.

The legislation will now be subjected to the amendment process, where Rubio said he is hoping to make the improvements he talked about in the video.

The House, meanwhile, is expected to unveil a separate bipartisan immigration reform bill even as GOP lawmakers also move separate pieces of immigration reform legislation through the committee process.

The woman whose letter Rubio responded to said that like many House Republicans she would prefer passing reforms in smaller, separate bills.