More than one thousand Boeing Delta rocket workers hit the picket lines this morning, snarling plans to launch a critical U.S. national security satellite and environmental research spacecraft.

Differences over health benefits and retirement plans remained unsolved despite recent talks between Boeing and the International Association of Machinists and Aerospace Workers.

The union includes 365 workers at the Delta program's lead Huntington Beach facility in California, plus 288 at Cape Canaveral and 100 at Vandenberg Air Force Base launch sites. The strike also affects workers at the rocket manufacturing plant in Decatur, Alabama.

Union members voted to reject Boeing's offer for a three-year contract, citing the company's desire to cut retiree health care coverage for new workers, among other complaints.

Boeing says the contract included pay hikes and improved pensions.

Attempts by a federal mediator to renew discussions between both sides on Tuesday failed to reach a consensus.

The strike began at 12:01 a.m. EST (0501 GMT) today.

Caught in the crossfire are several Delta rockets standing on launch pads at Cape Canaveral and Vandenberg. Already delayed because of the strike is NASA's mission to place a pair of atmospheric research satellites into orbit from California. That launch had been scheduled for November 7, but was called off last week because the space agency didn't want its payloads sitting on the pad during a strike. As a result, the spacecraft were left inside a processing hangar instead of being moved to the pad for mating to the rocket last Monday has scheduled.

Also at Vandenberg is a larger Delta 4 rocket that is supposed to haul a U.S. National Reconnaissance Office spy satellite cargo into orbit by year's end. It too is waiting for the payload to be brought out to the pad.

Meanwhile, a Delta 4 at Cape Canaveral has the GOES-N weather satellite already mounted aboard for launch sometime this month. Because this launch campaign has progressed much further than the other two waiting at Vandenberg, Boeing says the company is looking to see if the union members are still needed for any remaining pre-launch preparations.