Some striking Providence nurses appeared unwilling to accept the tentative labor agreement reached with the health system this week, raising the possibility that the largest health care strike in Oregon history could continue into a fifth week.

Providence hospitals reached a tentative contract agreement with the health system’s leaders late Tuesday, nearing a possible end to a strike that was in its 26th day.

An apparent breakthrough in the nearly month-long strike at Providence hospitals was reached Tuesday night as both Providence officials and the Oregon Nurses Association announced a tentative deal at all eight locations affected.