FORT WORTH, Texas (AP) — Federal mediators have rejected a union’s request that could have cleared the way for a year-end strike by flight attendants at American Airlines.

The National Mediation Board instead directed the airline and the Association of Professional Flight Attendants to keep negotiating over a new contract.

“We look forward to continued negotiations with APFA and reaching an agreement our flight attendants have earned,” American said in a statement Tuesday.

Union President Julie Hedrick said in a statement that despite the setback, “we are not backing down. We will intensify our pressure on the company.”

Hedrick said American “continues to drag out bargaining with contract proposals that do not address the current economic environment.”

Flight attendants voted to authorize a strike and picketed outside American’s headquarters, saying that they have not received raises since 2019. The two sides remain far apart in negotiations.

The union seeks raises of 35% followed by two yearly increases of 6%. American is offering an immediate raise of 11% upfront followed by annual increases of 2%. The airline says its proposal to pay flight attendants during boarding would make the 11% raise more like 18%. American, which is based in Fort Worth, Texas, is proposing to match Delta’s decision last year to pay flight attendants during boarding.

Under a federal law that covers the airline and railroad industries, there are several obstacles that make it very hard for union workers in those industries to go on strike.

One of those hurdles is getting federal mediators to declare an impasse in negotiations, which starts a 30-day “cooling-off” period after which a strike is possible.

The mediators rarely declare an impasse. Even if they do, the law allows the president to delay a strike and Congress to impose settlement terms on both sides.