Federal mediators told negotiators in the Northwest Airlines pilots' strike to take Labor Day off, urging both sides to rethink their positions after "exploratory" talks yielded no progress in ending the 10-day-old walkout.

Officials for Northwest and the Air Line Pilots Association, the union representing the striking pilots, met separately with mediators at a suburban Chicago hotel over the weekend to determine whether full-blown negotiations were possible. Mediators shuttled between the two sides, then sent them home Sunday."Given the differences that now exist between the parties on substance, the National Mediation Board has asked the parties to reconsider their respective positions and alternatives," board chairwoman Maggie Jacobsen said in a statement.

It said weekend talks "involved possible parameters of a settlement," but gave no details. Mediators have asked both sides to refrain from talking to the media.

In an interview Monday on NBC's "Today" show, Labor Secretary Alexis Herman said she considered it good news that the two sides met all day Saturday and Sunday. "We're hopeful they'll get back to the bargaining table and settle their differences," she said.

Discussions are scheduled to resume Tuesday in Minneapolis, although officials could not say whether the two sides would meet face to face.