Originally published by the Voice of America (www.voanews.com). Voice of America is funded by the US Federal Government and content it exclusively produces is in the public domain. Iraqi, US forces Step Up Baghdad Security Crackdown --------------------------------------------------- http://enews.voanews.com/t?ctl=1640503:A6F02AD83191E1602497710CFC16F4DF9574F7DCC14957C0 Iraqi Prime Minister Nouri al-Maliki announced official beginning of new security plan Wednesday Iraqi and U.S. forces have stepped up joint patrols in Baghdad as part of a new security crackdown to stem sectarian and insurgent violence in the city. Nouri al-Maliki speaks in Karbala, 14 Feb 2007Troops set up new checkpoints across the city and started search and clearing operations Wednesday, when Iraqi Prime Minister Nouri al-Maliki announced the official beginning of the new security plan. A top Iraqi military officer involved in the plan said the country's borders with Iran and Syria will be sealed for 72 hours as part of the crackdown. Meanwhile, the U.S. military is standing by its assertion that radical Shi'ite cleric Moqtada al-Sadr has gone to Iran. But Sadr aides insist the Shi'ite leader is in Iraq and has reduced public appearances for security reasons. In other developments, the U.S. military says six U.S. soldiers have been killed in a series of incidents since Tuesday. Also, U.S. Major General William Caldwell says "sophisticated weaponry" brought down a U.S. Marine helicopter last week in al-Anbar province. The crash killed all seven U.S. personnel on board. Some information for this report was provided by AP, Reuters and AFP .