AMMAN, Jordan - Jordan and Yemen offered troops to Iraq - a major policy shift that could be an attempt to encourage other Arab and Muslim nations to help the country's new U.S.-backed government restore security. But the risks are considerable if Jordan and Yemen are seen taking up arms against the Iraqis, or if Iraq's neighbors, like Turkey and Iran, which already have influence or ambitions in that country, follow their lead and offer forces. Iraq's new authorities have been opposed to neighboring states, particularly Iran, Turkey and Syria, sending in troops. But the offers from Iraq's western neighbor,...