Six Republican senators have sent Harry Reid a blistering letter, urging him to block any executive action that would amount to immigration amnesty.

The letter, co-written by Sen. Jeff Sessions (R-Ala.), says that executive action on immigration would be illegal.

“President Obama will be exercising powers properly belonging to Congress if he makes good on his threat,” the letter said.

The letter warns that lawmakers will use all procedural means necessary to resolve the constitutional crisis that the president would create.

“We have got to make sure that Congress speaks on this issue,” Sessions told Megyn Kelly tonight.

“The American people have pleaded with Congress and presidents for 30 years. They’ve asked, pleaded, and demanded really a lawful system of immigration that serves the national interests. President Obama is decimating law enforcement, Megyn, in a host of ways. This is just one of them,” he said.

Watch more above.