MADISON, Wis. (AP) -- Wisconsin's Commerce Secretary Jack Fischer is resigning effective Friday.

Fischer's resignation announced on Wednesday comes just 10 days after the Milwaukee Journal Sentinel reported that Fischer and a top aide billed taxpayers $21,282 for three international trips in less than three months this spring.

Fischer does not give a specific reason for his resignation. But he says it has become increasingly difficult to carry out the department's mission and he does not want to stand in the way of continuing progress.

Gov. Jim Doyle issued a statement thanking Fischer for his service. Doyle spokesman Lee Sensenbrenner says the governor did not ask for Fischer's resignation.