N.F.L. owners and players continued to negotiate late Thursday evening, but progress slowed as time dwindled for striking a labor deal that would avoid the disruption of the preseason.

The N.F.L. had hoped to have at least an agreement in principle in place around the Fourth of July, but three people who have been briefed on the negotiations said that although a resolution remained possible within the next 10 days, it was more likely that negotiations would drag on past that time, with a better chance for a settlement coming the week of July 10.

One person said that little progress on the critical issues that divide the sides had been made earlier this week, when lawyers and staff members negotiated without owners and players in attendance, and another said he still believed it was possible that games would be missed and that it would require a breakthrough for a deal to be completed in the next couple of weeks.

The sides met until past midnight in Minnesota Thursday -- a 15-hour negotiating session -- which restored some hope that a deal was still within reach next week, after it appeared negotiations had suffered a setback earlier in the day.