BOSTON (AP) — The Boston Symphony Orchestra says it agreed with its musicians to a 48-hour extension of their collective bargaining agreement, allowing more time for negotiations to head off what could be the first strike in the ensemble’s 145-year history.

The Boston Musicians’ Association said Saturday it had authorized a strike ahead of the expiration of the union’s three-year contract at 11:59 p.m. Sunday. The BSO said Sunday the contract had been extended to 11:59 p.m. Tuesday.

BSO CEO Chad Smith said Sunday that the extension had been agreed to pending a ratification vote by the Boston Musicians’ Association and the Boston Symphony Orchestra Players’ Committee, a sign there could be progress toward an agreement for a contract. The unions did not respond to a request for comment.

The orchestra and management have had strained relations since BSO decided in March to force out music director Andris Nelsons next summer after 13 seasons.

The orchestra’s season is scheduled to open Sept. 17.