BRUSSELS, July 26 (Reuters) - Qatar has threatened to cut off gas supplies to the European Union in retaliation for the bloc's due diligence code on forced labor and environmental damage, according to a letter from Qatar to the Belgian government seen by Reuters.

Qatar is the world's third-largest exporter of liquefied natural gas (LNG), after the United States and Australia. It has provided Europe with between 12 and 14 percent of its LNG supplies since Russia's invasion of Ukraine in 2022.

In a letter to the Belgian government dated May 21, Qatari Energy Minister Saad Al-Kaabi said his country is responding to the European Union's Corporate Sustainability Due Diligence Directive, which requires major companies operating in the bloc to monitor and address human rights and environmental issues in their supply chains.

"Simply put, if further changes are not made to the Corporate Sustainability Due Diligence Directive, the State of Qatar and QatarEnergy will have no choice but to seriously consider alternative markets outside the EU for our LNG and other products, which offer a more stable and welcoming business environment," the letter read.

A spokesperson for Belgium's representation to the European Union declined to comment on the letter, which was first published by the German newspaper Welt am Sonntag.

(Prepared by Duaa Mohammed for the Arabic edition - Edited by Marwa Salam)