UN officials say Iraq has broken its promise to increase co-operation with weapons inspectors.
They claim Saddam Hussein has become determined to resist UN monitoring following the criticism of the US at last week's Security Council meeting.
No scientist involved in biological, chemical or missile technology has granted a private interview with the inspectors since February 7th.
UN officials also say they have not received crucial documents about past weapons programmes.
This is despite an Iraqi promise to set up a commission to search for evidence needed by the inspectors.
"They are feeling 'The world opinion is with us. We can resist further pressure. We have time. We can play with the US and UK'," a UN official told the Washington Post.
"This is very dangerous. We have not seen any positive moves on the part of Iraq."
Unless Saddam moves quickly, chief weapons inspector Dr Hans Blix is expected to deliver a downbeat assessment of Iraqi co-operation in his next report to the Security Council, which could provide a justification for war.
The UN resolution requires Iraq to provide "private access" to anyone the inspectors wish to interview, but so far monitors have only been able to speak alone to three scientists.
Meanwhile, the Washington Timesreports US military planners are now looking at mid-March as a starting date for launching an invasion of Iraq. The delay has been caused by diplomatic snags and difficulties in moving heavy Army divisions into the Persian Gulf.