WELLINGTON, New Zealand (AP) — For decades, the tiny Marshall Islands has been a stalwart American ally. Its location in the middle of the Pacific Ocean has made it a key strategic outpost for the U.S. military. But that loyalty is being tested amid a dispute with Washington over the terms of its “Compact of Free Association” agreement, which expires soon. The U.S. is refusing to engage the Marshallese on claims for environmental and health damage caused by dozens of nuclear tests it carried out in the 1940s and 1950s. The dispute has some U.S. lawmakers worried that China might be willing to step into the breach, adding to a bruising competition for geopolitical dominance between the two superpowers.