Trent Lott, R-Mississippi, is serving in his fourth term in the U.S. Senate.
WASHINGTON (CNN) - Sen. Trent Lott, R-Mississippi, intends to resign by the end of the year and join the private sector, sources tell CNN.
Lott is set to reveal his plans at a 12 p.m. ET news conference in Pascagoula and a 4 p.m. ET news conference in Jackson.
Lott decided to run for a fourth Senate term in 2006 for reasons including representing Mississippi and the Gulf Coast region in the wake of Hurricane Katrina.
He now feels he's laid the groundwork in Washington to make sure the region is looked after, according to a source familiar with his announcement.
A senior Republican source close to Lott said one reason for the decision
is the new lobbying restrictions on former lawmakers.
A new law kicks in on January 1, forbidding lawmakers from lobbying for two years after leaving office. Those who leave by the end of 2007 are covered by the previous law, which demands a wait of only one year.
Mississippi's GOP Gov. Haley Barbour will appoint a temporary replacement, who will serve through 2008. A special election will then be held to determine who will serve the remainder of Lott's term.
Reps. Chip Pickering and Roger Wicker are the leading candidates to succeed Lott. But the talk is that Pickering, who announced earlier this year he intends to leave Congress, would turn down the job.
Lott is the Republican Whip in the Senate and his resignation will bring to an end more than three decades in Congress.
Lott won a House seat in 1972 and was elected to the Senate in 1988. He's currently in his fourth term.
He is the first person to be elected whip in both the House and Senate.
– CNN's John King, Mark Preston, and Dana Bash