President Barack Obama promised Monday to work with other nations "to halt the rise of piracy," while Somali pirates vowed revenge for the deaths of three colleagues shot by snipers during the daring high-seas rescue of an American sea captain. The pirates' threat raised fears for the safety of some 230 foreign sailors still held hostage in more than a dozen ships anchored off lawless Somalia. Sunday's nighttime operation was a remarkable achievement for snipers on a rolling warship in choppy seas, but few experts believe the victory will quell a rising tide of attacks in one of the world's busiest shipping lanes. One of the American sailors whose captain was rescued after the five-day standoff urged Obama on Monday to take the lead in ending the scourge of piracy. "It's time for us to step in and put an end to this crisis," he said. "It's a crisis, wake up," said Shane Murphy, chief mate aboard the US-flagged Maersk Alabama.