Nicolás Leoz, the most powerful man in South American soccer for more than two decades, who had spent recent years under house arrest in Paraguay fighting extradition to the United States on corruption charges, died on Wednesday. He was 90.

The cause was cardiac arrest, his lawyer, Ricardo Preda, said.

Mr. Leoz was the president of Conmebol, South America’s soccer confederation, from 1986 to 2013. He was also a longtime top executive of FIFA, international soccer’s governing body, which saw its leadership upended by a sweeping criminal case announced by the United States Justice Department in 2015. He was one of more than 40 men charged as part of that inquiry.

In a federal indictment, unsealed in May 2015, American prosecutors accused Mr. Leoz of repeatedly soliciting and accepting six- and seven-figure bribes, engaging in schemes dating to 1991 that had diverted revenue from international soccer into his own pocket. To help justify their investigation, the prosecutors pointed to Mr. Leoz’s use of a New York-based financial adviser to manage an investment portfolio worth $40 million.

Among Mr. Leoz’s legacies at Conmebol was his relocation of that organization’s headquarters to Luque, Paraguay, near Asunción, where he won sovereign-territory status from national lawmakers — granting the headquarters legal immunity in the style of an embassy.