U.S. Trade Representative Ron Kirk said Tuesday that he intended to step down as the top U.S. trade official in late February.

"It has been no less than my greatest professional privilege to serve President Barack Obama alongside the dedicated professionals of USTR (Office of the U.S. Trade Representative)," Kirk said in a statement which gave no clues of his future plans or successor.

Kirk is leaving after nearly four years of service on the trade front. He has led the Obama administration's market-opening negotiations and dialogue with U.S. trading partners, including the conclusion and congressional passage of bilateral free trade agreements with South Korea, Panama and Colombia.

In statement late Tuesday, Obama expressed his gratitude to Kirk for his "hard work" over the past four years.

"From bringing home new trade agreements with Korea, Colombia and Panama and negotiating to open up new markets for American businesses, to cracking down on unfair trade practices around the world, he has been a tremendous advocate for the American worker," Obama said.