Updated: 3:44 pm ET
Arizona Sen. Jon Kyl announced on Thursday that he will not seek re-election in 2012.
Kyl, a three-term senator and the Senate's Republican Whip, announced the decision at a press conference on Thursday.
"My heart says it's time," Kyl said. "This is a great job, I think nothing beats it, just at a certain point it's time to leave. "
"There is no other reason than the fact it is time," he added, of his decision to retire. "It is time for me to do something else and time to give someone else a chance."
He said he plans to use the remainder of his term to work on tough issues without the political pressures associated with re-election, and said he means to form a coalition with other departing senators as a means to do so.
"Some people stay too long, and there are other things to do in life," Kyl said. "I never expected to be in office for 26 years."
(Watch video of his remarks below.)
Kyl is the fifth senator to announce his impending retirement from the Senate: Sen. Joe Lieberman (I-Conn.), Kent Conrad (D-N.D), Jim Webb (D-Va.) and Kay Bailey Hutchison (R-Texas) made public similar decisions in recent weeks.
Following Kyl's resignation, fellow Republican Arizona Sen. John McCain released a statement noting that serving with him had been "an honor and a privilege," and that "he will be sorely missed."
Republican Arizona Rep. Jeff Flake added that the departure of Kyl, whom he called a mentor and friend, "will create a huge void."
"Senator Kyl is the quintessential workhorse," Flake said. "With his retirement, Arizona will lose a tireless advocate, the country will lose a stalwart on national defense and foreign affairs, and Republicans will lose a lodestar in the Senate."
In remarks at the Conservative Political Action Conference (CPAC) on Thursday, Sen. Minority Leader Mitch McConnell, of Kentucky, called Kyl's impending departure "a big loss for the country."
National Republican Senatorial Committee (NRSC) Chairman John Cornyn added that he was confident Republicans would retain the seat.
"I am also confident that this seat will remain in Republican hands," he said in a statement. "It's clear that no matter who the Democrats nominate, that person will find it very hard to sell voters on the Democrats' agenda of reckless spending in Washington, and their failure to create jobs while driving our national debt past $14 trillion."
The departure of Kyl will mark the first time since 1994 that there will not be an incumbent running for Senate from Arizona.
Flake and the Democratic Homeland Security Secretary Janet Napolitano (formerly the Arizona Governor) are both considered a possible contenders in what will surely become a competitive race for the open seat.
The Washington Post reports that, prior to January's mass shootings in Tucson, Arizona, Democratic Rep.
Gabrielle Giffords was planning a possible Senate bid.
"Prior to the tragedy, she had decided that if Kyl retired, she would run," a source close to Giffords told the Washington Post. The source noted that Giffords did not expect Kyl to retire.