Jan. 1 (Bloomberg) -- The U.S. ceded security control of Baghdad’s Green Zone, while the U.K. handed over Basra airport to Iraqi authorities as part of agreements that came into effect today.

“It is our right to consider this day the day of sovereignty and the beginning of the process of retrieving every inch of our nation’s soil,” Iraqi Prime Minister Nuri al-Maliki said in a ceremony held at a palace in central Baghdad previously used by executed dictator Saddam Hussein, Agence France-Presse reported today.

Iraq’s parliament approved a security accord on Nov. 27 that provides for the withdrawal of U.S. forces by the end of 2011. The pact calls for American troops to pull back from Iraq’s towns and cities by mid-2009 and curbs U.S. powers to detain Iraqi citizens and conduct military operations.

The U.S. had about 145,700 troops stationed in Iraq as of Dec. 30, according to a U.S. military spokeswoman in Baghdad today who declined to be identified, citing regulations. The number reached about 166,000 at the height of the so-called “surge” that began in 2007. There were about 137,000 troops in Iraq in January 2007.

Britain’s withdrawal from Basra airport follows a plan to wrap up major operations in Iraq early in 2009. The U.K. had about 4,100 troops in Iraq as of Dec. 10, most at an air base outside Basra, down from more than 40,000 at the time of the U.S.-led invasion in 2003.

To contact the reporter on this story: Howard Mustoe in London at hmustoe@bloomberg.net; Fiona MacDonald in Kuwait FmacDonald4@bloomberg.net

Last Updated: January 1, 2009 13:18 EST