By Patricia ZengerleWASHINGTON, March 10 (Reuters) - Democratic U.S. senators expressed alarm on Tuesday about the Iran war, saying they were worried that President Donald Trump could deploy U.S. ground forces and noting the high risks given Russian support for Tehran's military."We know that Russia is already helping with intel, providing that to Iran, and that there's an axis with Russia and China, Iran and North Korea that puts at greater risk the United States and our national security," Dem...