Contract talks between Delta Air Lines Inc. and its pilots have been suspended for three weeks by a federal mediator because of a lack of progress. The two sides were notified of the break Aug. 3 by the National Mediation Board, according to a letter posted on the union’s website from John Malone, chairman of the Air Line Pilots Association at Delta. The hiatus will allow each side to assess its bargaining position and goals for the talks, he said. “On the negative side, this is an indication that the NMB believes our efforts at working towards a deal have stalled,” Malone said in the letter. “On the positive side, this is an opportunity for all of us to pause, step back and consider what we want to accomplish in these negotiations.” The federal panel is scheduled to meet with Delta and union negotiators Aug. 26 in Washington to determine if each is ready to resume talks. “Delta is committed to reaching a timely new agreement that is market-based, sustainable, and that also ensures Delta pilots have an industry-leading package of pay, benefits and work rules,” the carrier said by e-mail. The mediation board didn’t immediately respond to a request for comment. The aviators rejected a tentative agreement in July 2015, and a mediation board member joined talks earlier this year. The union represents 13,000 Delta employees. The pilots initially proposed a raise of almost 40 percent, compounded over three years. Delta said earlier this year that the plan “does not provide a reasonable framework for negotiations.”