U.N. chief weapons inspector Richard Butler said Sunday that Iraq is cooperating in opening sensitive sites to his teams, and he hopes the Iraqis will follow that up by volunteering information about banned weapons materiel.

Butler, in Baghdad to oversee two weeks of weapons inspections, said the Iraqis "have shown us remarkable cooperation" since President Saddam Hussein and U.N. Secretary-General Kofi Annan agreed a month ago to open up previously off-limits sites. The agreement averted a U.S. military strike.But Butler said on CNN's "Late Edition" that cooperation is not enough to verify that Iraq has destroyed its weapons of mass destruction as required under U.N. resolutions approved at the time of the 1991 Persian Gulf War.

He said he won't withdraw his current contention that Iraq is still hiding biological and chemical weapons "just because they say `trust me.' That's really bad arms-control practice."

Butler, an Australian, said that along with good cooperation in the field, the Iraqis have been volunteering a "little bit" of information about their weapons program.

Butler said over the next two weeks his team will carry out "base-line inspections" on 1,058 buildings at eight presidential sites opened to inspectors by the Annan-Saddam agreement.