Sen. Ted Cruz (R-Texas) and five other Republican senators on Wednesday threatened to use "all procedural means necessary" to force the Senate to take action against President Barack Obama's plan to grant amnesty to millions of illegal immigrants.

The Republicans wrote to Senate Majority Leader Harry Reid (D-Nev.) to warn that the Senate must take action to stop Obama from violating Congress's right to set immigration policy. The letter said they would work with Reid to stop Obama, but warned of consequences if Reid does nothing.

Sen. Ted Cruz (R-Texas) and other Republicans are threatening to use any means necessary to force a vote opposing Obama's immigration plan. (AP Photo/Manuel Balce Ceneta, File)

"[S]hould you decline to defend the Senate and the Constitution from executive overreach, the undersigned senators will use all procedural means necessary to return the Senate's focus during the lame duck session to resolving the constitutional crisis created by President Obama's lawless amnesty."

The letter was signed by Sens. Mike Crapo (R-Idaho), Mike Lee (R-Utah), Pat Roberts (R-Kan.), Jeff Sessions (R-Ala.), and David Vitter (R-La.).

While the letter didn't say specifically what they might do, Congress will have to pass some kind of spending bill when it returns in the coming days. The letter could therefore signal that the GOP will oppose funding for the government until the immigration issue is addressed.

Cruz himself has taken steps to filibuster Senate activities, and might again.

Obama and Democrats in the Senate suffered a major defeat in Tuesday's midterm elections, which has prompted some speculation about whether Obama would move ahead with his plan to let millions of illegal immigrants stay in the U.S. and find work.

Obama's plan was delayed in the hopes that it would help Democrats at the polls, a plan that seems to have backfired. Obama is expected to speak to reporters later Wednesday afternoon about his reaction to the elections.

Reid will no longer be Senate Majority Leader in the 114th Congress. But unless Obama announces a new delay, the threat of Obama's action is looming over the next few weeks during the lame duck session of the 113th.