The former executive director of an Alaska nurses union has agreed to plead guilty to a federal charge of embezzling more than $22,000 from the union to pay his personal bills, according to documents filed in court this week.

Thomas Renkes is facing up to five years in prison on a felony charge of embezzlement of union funds, according to court documents.

According to a plea agreement with prosecutors, Renkes was the executive director of the Alaska Nurses Association between October 2007 and August 2008. The association is a labor union that represents nearly 1,000 nurses at Alaska hospitals, including Providence Alaska Medical Center and Central Peninsula General Hospital in Soldotna.

Renkes was a salaried employee of the union, paid by union member dues, the documents say. But prosecutors allege he was also taking money on the side, using a union credit card to go shopping and to buy plane tickets for his family.

In the course of his employment, he racked up more than 80 unauthorized purchases on the card for more than $22,500, prosecutors say.

Renkes paid the credit card bills using union checks he fraudulently received by providing false and misleading justifications for the personal expenses, they say. In one case, he paid for a $1,500 personal legal expense and then told the union that the charge was for "ANA legal issues with other states," the plea agreement says.

The plea agreement says the parties haven't reached an agreement on the sentence Renkes will receive after his plea hearing June 3.