WASHINGTON (AP) -- More than 1,000 government employees, including hundreds of police officers, have been convicted over the last two years in FBI corruption cases against crooked public officials, Director Robert Mueller said Wednesday.

In prepared testimony to the Senate panel that oversees the bureau, Mueller called public corruption cases the FBI's "top criminal investigative priority."

Public corruption "erodes public confidence and undermines the strength of our democracy," Mueller said in his testimony. "Unchecked, it threatens our government and our way of life."

Mueller was to appear Wednesday morning before the Senate Judiciary Committee in one of its last hearings before Democrats take control of the panel next year. His remarks also outlined strides the FBI has taken to protect the nation against terror attacks since 2001.

Over the last year, the Justice Department has targeted about a dozen high-profile House and Senate lawmakers in corruption cases - including three Republicans in the month before the Nov. 7 election that shifted power in Congress to Democrats.

Overall, 177 federal officials have been convicted in corruption cases over the last two years, Mueller said. During the same time, the FBI investigated cases against 158 state officials, 360 local officials and more than 365 police officers. It was not immediately clear how many police officers represented local, state or federal law enforcement agencies.

Last year alone, the FBI saw a 25 percent rise in its public corruption investigations, resulting in 890 indictments and 759 convictions, Mueller said. There are 2,118 cases still pending, he said.

A chunk of the cases were the result of a Phoenix-based sting, code-named Operation Lively Green, which Mueller said so far has targeted 99 suspects in a bribery investigation of cocaine trafficking across the U.S.-Mexican border. More than 70 military personnel, prison guards and other law enforcement workers so far have been convicted of taking bribes to help move several hundred kilograms of cocaine across the border to Phoenix and Las Vegas, sometimes wearing uniforms and using military vehicles.