India has filed a complaint with the World Trade Organization challenging the U.S. system for handing out temporary work visas to foreigners, a program that has become a lightning rod for criticism in the U.S. presidential campaign.

The complaint, lodged on Thursday, challenges increased fees charged by the U.S. for certain types of visas available for highly skilled workers, the WTO said. India’s information technology companies with operations in the U.S. have been among the most frequent users of these visas, bringing tens of thousands of Indian workers to the U.S.

The U.S. passed a law last year that doubles the fees to $4,000 and $4,500, depending on the kind of visa. Republicans and Democrats had both criticized the program for allowing companies to replace U.S. workers with cheaper labor from developing nations, such as India.

Despite the changes, presidential candidates from both parties have continued to attack the visas. Donald Trump, the Republican front-runner, said at a debate Thursday night that he supported giving more visas to highly skilled foreign workers. But after the debate, he called one of the visas, the H1-B, a “cheap labor program” and pledged to “institute an absolute requirement to hire American workers first for every visa and immigration program.”

India’s complaint to the WTO starts a 60-day period in which the two sides can negotiate. After that, India has the right to ask the Geneva-based arbiter of trade disputes to rule on its complaint.