Sen. Trent Lott of Mississippi, the No. 2 Republican in the Senate, will announce his resignation effective this year, FOX News has learned.

Lott, 66, was re-elected in 2006 amid speculation that he would retire. Instead, against his wife Tricia's wishes, he ran again, regaining a Senate leadership position after being forced from the top Republican seat in 2002, following remarks he made that were seen as racially insensitive.

Lott, who is serving his fourth Senate term, was expected to discuss his plans later Monday.

Lott becomes the sixth Senate Republican this year to announce retirement, possibly posing more difficulties for an embattled GOP that will be trying to retain the presidency and fight further losses to Democrats who regained control of both houses of Congress last November.

His leaving also will create an open Republican leadership slot, but FOX News has learned that Sen. Jon Kyl of Arizona will make a run for that spot.

Lott's decision to remain in the Senate last year was aimed in part at using his clout to push for repairs to his state's coastal region after the wrath left by the 2005 hurricane season, including hurricanes Katrina and Rita. Lott's own coastal home was destroyed by the storms.

Two senior Republican aides tell FOX News that Lott has informed a small inner circle of colleagues about his plans.

The senator, after 34 years of public service in Congress, is not wealthy like many of his colleagues and has talked for some time about leaving so he could earn more money.

So, aides said, the senator decided to leave by year's end to circumvent new lobbying rules — instituted by Congress this year and effective in 2008 — that that would bar members from lobbying their colleagues after two years.

The so-called "revolving door" policy in effect now keeps former members from lobbying their colleagues for one year. The changes were made in the wake of the scandal surrounding former lobbyist Jack Abramoff.

Mississippi Gov. Haley Barbour, R, must appoint a replacement for Lott within 10 days of his leaving office, and candidates will vie for the seat in next November's elections. Whoever wins would serve out the remainder of Lott's term, which ends in 2012.

In his Senate position, Lott is the whip, or vote-counter-in-chief, second in GOP seniority only to Minority Leader Mitch McConnell. The position — to which he was elected by his Republican colleagues — was a sign that Lott had been forgiven for the remarks four years earlier during the 100th birthday celebration for then South Carolina Sen. Strom Thurmond, who ran for president in 1948 on a segregationist platform.

At the event, Lott said Mississippi voters were proud to have supported Thurmond's candidacy, and added: "If the rest of the country had followed our lead, we wouldn't have had all these problems over all these years either."

A few days later, Lott issued a statement saying he had made "a poor choice of words" that "conveyed to some the impression that I embraced the discarded policies of the past. Nothing could be further from the truth, and I apologize to anyone who was offended by my statement."

Lott's many apologies were to no avail. He lost the support of President Bush, who said his comments did not "reflect the spirit of our country."

Lott later wrote in a book — "Herding Cats: A Life in Politics" — that President Bush hurt his feelings by disavowing the comments in a tone that was "devastating ... booming and nasty."

FOX News' Trish Turner and The Associated Press contributed to this report.