Sen. Mike Lee (R-Utah) was involved in bipartisan negotiations over immigration reform early in the discussions. But he wasn't in the group that unveiled the proposal Monday. Why not? He disagrees with the proposed path to citizenship for undocumented immigrants.

“These guidelines contemplate a policy that will grant special benefits to illegal immigrants based on their unlawful presence in the country. Reforms to our complex and dysfunctional immigration system should not in any way favor those who came here illegally over the millions of applicants who seek to come here lawfully," Lee said in a statement. "Additionally, the framework carves out a special exception for agricultural workers that has little justification."

Lee has gotten involved in immigration reform in hopes of pushing smaller changes that would streamline the legal immigration system. He worked with Sen. Chuck Schumer (D-N.Y.) in 2011 on a plan that would give foreign real estate investors residency.

But during his 2010 campaign Lee promised not to support "amnesty" for undocumented immigrants and he reaffirmed that promise when he joined the working group in December. Both Democrats and Republicans in the Gang of Eight have made clear that a path to citizenship is key to a deal.

Utah, one of the most conservative states in the country, has forged its own compromise on immigration that includes both increased enforcement and a guest worker program.

In his statement, Lee said he would continue to work on his own proposals.