The agency formerly known as the Immigration and Naturalization Service also said the total number of pending cases that exceeded the six-month wait period fell from 3.8 million in January 2004 to 1.1 million in July this year.
"It really is a Herculean achievement that we've been able to achieve this," Emilio Gonzalez, the agency's director told reporters.
Nearly 1 million applications will still be pending at the start of October, said Michael Ayetes, director of USCIS field operations.