Speculation has been mounting over whether Donald Trump will fire attorney general Jeff Sessions or special counsel Robert Mueller (AP)

Members of the US Senate Judiciary Committee are working on legislation that could attempt to insulate special counsel Robert Mueller from being fired.

A Republican and two Democrats said they are among committee members working on legislation that would prevent the firing of special counsels without judicial review.

They are Republican senator Lindsey Graham of South Carolina and Democrats Sheldon Whitehouse of Rhode Island and Richard Blumenthal of Connecticut.

A spokesman for Mr Graham said the senator is still working on the bill and it is unclear when it will be introduced.

Mr Graham has sternly warned US President Donald Trump not to fire Mr Mueller or Attorney General Jeff Sessions.

He said there would be "holy hell" to pay if Mr Trump fired Mr Sessions.

PA Media