President Barack Obama welcomed the decision, saying the U.S. would stand by the Yemeni people “as they embark on this historic transition.” Saleh signed the U.S.-backed power-transfer deal; (ending his 33-year rule), brokered by neighboring countries, Wednesday in the Saudi capital Riyadh in exchange for immunity from prosecution. If the deal holds, he’ll be the fourth leader to lose power in the wave of Arab Spring uprisings this year, following longtime dictators in Tunisia, Egypt and Libya.