WASHINGTON (CNN) -- Rep. Tom Tancredo of Colorado said Tuesday he will add his name to the growing list of Republicans officially exploring a White House bid in 2008.

Tancredo said in a written statement that he will file papers "this week" with the Federal Election Commission to form an exploratory committee, but a Tancredo spokesman added that the committee's activities will officially begin effective immediately as is permitted under federal election law.

Tancredo, most known for his support of strict immigration reform, indicated that the controversial issue would be a major focus his potential presidential bid.

"I am considering this campaign because of my commitment to real immigration reform: reform that first and foremost is dedicated to the security and well-being of the citizens of the United States, and to respect the rule of law in our beloved nation," Tancredo wrote in a letter to his supporters posted on his new website -- www.teamtancredo.com

"After a lot of prayer, and long talks with my wife Jackie and our children, I have decided I am willing to put myself forward as a candidate for president in order, above everything else, to advance our immigration reform agenda, and to reclaim the Republican Party for its core conservative values," Tancredo added.

-- CNN's Robert Yoon and Alexander Mooney