Secretary of State Colin Powell said Tuesday that weapons inspectors should not be allowed to return to Iraq without a tough, new U.N. resolution.

Powell, clashing with the chief U.N. weapons inspector in his short speech at a hastily arranged news conference, said sending inspectors back to Iraq now after a lapse of nearly four years would risk further deception by President Saddam Hussein.

Chief U.N. weapons inspector Hans Blix reached agreement with Iraq earlier Tuesday in Vienna to resume the inspections.

But Powell, in an unusual diplomatic confrontation, said "Dr. Blix is an agent of the Security Council and will carry out what the Security Council will do."

"Our position," Powell said, "is that he should get new instructions in the form of a resolution."

And, Powell said pointedly, the Security Council will adopt its resolution without negotiating with Iraq.

"We will not be satisfied with Iraqi half-truths or Iraqi compromises, or Iraqi efforts to get us back into the same swamp that they took the United Nations into," Powell said.

Sending inspectors back to Iraq now after a lapse of nearly four years, Powell added, would risk further deception by President Saddam Hussein.

"Everybody understands that the old inspection regime did not work," Powell said. "They [the Iraqis] tied it up in knots."

Blix, in Vienna, said an advance team of U.N. inspectors could be in Iraq in two weeks if it gets a go-ahead form the Security Council.

The deal ignores U.S. demands for access to Saddam's palaces and other tough provisions of a resolution the United States and Britain have proposed jointly.

Referring to the other three Security Council members -- France, China and Russia -- which could veto the resolution, Powell said "other nations have a different point of view."

But he said inspections would work only if there is a resolution that "keeps the pressure" on Iraq by warning of consequences if it continues to defy the Security Council.

Stressing that the goal should be disarming Iraq, Powell said "there is no magic calendar as to when they [inspectors] have to go in. They should go back when they are able to do their job."

He said that was possible only with a new resolution with "new terms and high standards."

"We are determined," Powell said. "We are absolutely convinced we can make the case that a new resolution is appropriate with consequences for further violations."

The Iraqi chief negotiator, Amir al-Sadi, said at the meeting with Blix the issue of surprise inspections of Saddam's presidential sites, which encompass 12 square miles, was "not a subject on the agenda."

"Quite honestly I don't understand why it is so critical," al-Sadi said.

Al-Sadi said an advance party of weapons inspectors is expected to arrive in Baghdad in two weeks.

Asked if there would be access to the president palaces, the Iraqi negotiator said such visits were regulated by an agreement worked out between the United Nations and Iraq four years ago that required advance notice and the presence of international diplomats.

"It is regulated by a memorandum of understanding, and it is also referred to in Security Council resolutions and that remains valid," he said.

The restrictions on inspecting presidential sites would have to be lifted by the Security Council, something U.N. representatives in Vienna had emphasized throughout the two days of talks.

Mohamed El-Baradei, director general of the Vienna-based Atomic Energy Agency, the site of the talks, said the negotiations had resulted in "assurances from the Iraqis that we will have unconditional access to all sites," except the so-called presidential sites.

That apparently was an Iraqi concession, in that Baghdad had put a number of other sites off limits to surprise visits, including the headquarters of the Republic Guard and Defense Ministry.

Even as Powell was holding out for broader powers to the inspectors, three Democratic lawmakers who returned Tuesday from Iraq said the inspections must begin without delay and without either the United States or Iraq dictating the conditions.

Rep. David Bonior of Michigan said he and Reps. Jim McDermott of Washington and Mike Thompson of California tried to persuade Iraq to submit to unfettered inspections. "We pushed the government as hard as we could," Bonior said.

McDermott said U.S. officials should let the inspectors do their job before considering the use of force. "Then, we'll have the basis for making some other kind of decision," he said.

The Associated Press contributed to this report.