A team of U.N. weapons experts traveled Saturday to the northern city of Mosul to establish a new base, facilitating a broader range of inspections.
The new office "will serve as a convenient location to conduct inspections, particularly in the north," according to U.N. spokesman Hiro Ueki.
U.N. inspectors also visited three sites in and around Baghdad on Saturday and a fourth, the College of Agriculture, in the southern city of Basra, Iraqi officials said.
The three sites inspected around the capital were the Al-Abour Co., a maintenance arm of Iraq's Military Industrialization Corp.; the Al-Rasheed Co.'s Al-Mamoun Plant, which makes missile propellants and also was inspected Friday; and the Al-Khalis Alcohol factory, which had not been checked before.
Also on Saturday, Iraqi Foreign Minister Naji Sabri complained in a letter to U.N. Secretary-General Kofi Annan that the United States is violating international law by supporting mercenaries against the government of Saddam Hussein, according to the official daily Al-Iraq.
In his letter to Annan, Sabri cited funds allocated to Iraqi opposition groups and for military training of government opponents, saying these actions violated international charters guaranteeing the sovereignty of individual nations. He called U.S. support for Saddam's opponents an aggression on an independent state, Al-Iraq said.
The newspaper said the letter was delivered to Annan by Iraq's U.N. mission, but it did not say when.
The United States has funneled millions of dollars to Iraqi opposition groups in recent years, and President Bush recently authorized the U.S. Army to train opponents of Saddam's government.
Bush has threatened to use the American military to disarm Iraq if it does not give up its banned nuclear, biological and chemical weapons as required by U.N. Security Council resolutions. Iraq maintains it has no more banned weapons.
On Friday, Bush repeated his assertion that Iraq's Dec. 8 declaration to the Security Council that it has eliminated all illegal weapons was not credible. But he also said he only would wage war as a last resort.
Also Friday, Hans Blix, head of the U.N. inspectors searching Iraq for evidence of banned weapons, said the Iraqi government is cooperating with inspectors but there were several issues he wanted to raise during a Jan. 18 visit to the country.
He said there are "questions that have arisen as a result of (Iraq's) long declaration ... and we'd like to follow up some of those."
Blix said last month that Iraq's declaration had not provided sufficient details about its production of missile engines, recovery of 50 destroyed conventional warheads, the loss of 550 mustard gas shells, production and weaponization of the deadly VX nerve agent and its unilateral destruction of biological warfare agents.
On Friday in Kuwait, a U.S. congresswoman said Washington could not be sure Saddam does not have weapons of mass destruction unless U.N. inspectors interview hundreds of Iraqi scientists who worked on the country's arms programs.
Rep. Ellen Tauscher, a California Democrat and member of the House Armed Services Committee, said finding out what Iraq's scientists have done since U.N. inspections were suspended in 1998 was vital to getting the true picture of Saddam's arsenal.
The U.N. resolution that returned the inspectors to Iraq in late November allows private questioning of any Iraqi scientist and provides for them to be taken out of the country.
The Associated Press contributed to this report.