D.C. Mayor Vincent Gray refused Monday to discuss a report that he has declined repeated meeting requests from federal prosecutors who are probing his 2010 campaign, and he would not say if he stands by his promise to cooperate with authorities.

"I've indicated... all along, especially in the recent past, that it would really be inappropriate for me to comment on a pending investigation, and that continues to be my position," Gray said. "The investigation is ongoing, and we'll see it through."

The Washington Post, citing unnamed sources, reported in an editorial Sunday that Gray has refused "several" requests for interviews by authorities. The editorial called on Gray "to be more forthcoming about his knowledge of the events of 2010."

Three of Gray's campaign lieutenants have pleaded guilty to federal charges linked to improper payments to a minor mayoral candidate and the existence of a $653,800 "shadow campaign."

The long-running investigation has stained Gray's 22-month tenure, an era that has generally won plaudits for efficient city services and sound municipal finances, and sent his approval rating in to a freefall.

Gray has not said if he will seek re-election in 2014. He has vowed to finish his term, despite demands from three city lawmakers that he resign.

When the first allegations of impropriety became public in March 2011, Gray vowed to cooperate with any investigation. Asked directly by a reporter Monday if he was assisting authorities, Gray declined to comment.