WASHINGTON – President Bush vowed yesterday that the recent beheadings of Americans in Iraq would not sap the coalition’s resolve on the same day Iraq’s prime minister reversed a decision to release from jail two women involved in Saddam Hussein’s biological weapons programs.

Prime Minister Allawi’s statement seemed to quell fears in Washington that the new Iraqi government was willing to give in to the demands of terrorists who last week kidnapped two Americans and a British contractor, demanding the release of female prisoners from Abu Ghraib facility in particular.

Mr. Allawi told the Associated Press in an interview yesterday that he has not authorized the release of Rihab Rashid Taha, a scientist who became known as “Dr. Germ” for helping Iraq make weapons out of anthrax, and Huda Salih Mahdi Ammash, a biotech researcher known as “Mrs. Anthrax.”

Mr. Allawi’s statement appeared to reverse earlier remarks from the Iraqi Justice Ministry that announced that Ms. Taha would be released on bail after terrorists from a group called Tawhid and Jihad threatened to behead a British hostage if female prisoners were not released from the American-controlled prison of Abu Ghraib.

“We have not been negotiating and we will not negotiate with terrorists on the release of hostages,” Mr. Allawi told the wire. “No release takes place unless I authorize it.”

The prime minister Tuesday met with Mr. Bush at New York during the weeklong ceremonies of the opening of the United Nations General Assembly.

Some reporters questioned whether the meeting between the two leaders resulted in the decision to retain the two germ-weapons scientists. One coalition source told The New York Sun yesterday that the Americans in particular were “concerned about the optics” if Ms. Taha was released after two Americans were beheaded by terrorists demanding the release of female prisoners.

A statement from the American embassy in Baghdad said the two women were in American custody and that the “legal status of these two and many others is under constant review.”

The decapitated body of American contractor Jack Hensley was found in Baghdad yesterday in a black plastic bag after an Al Qaeda-affiliated Website announced that he had been killed because the demands of his kidnappers were not met. A video claiming to show his murder was posted on an Islamic Web site displaying a blindfolded man wearing an orange jumpsuit sitting in front of five masked terrorists dressed in black. White House spokesman Scott McClellan yesterday said the video “shows the true barbaric nature of the enemies we face in Iraq that they would take innocent civilian life…They will be defeated, they will not prevail.”

Mr. Hensley’s murderers, known as Tawhid and Jihad, are linked to the Jordanian terror master Abu Musab al-Zarqawi, who was trained in Afghanistan by Al Qaeda. They have claimed credit for the abduction and murder of seven people so far, including the American Nicholas Berg.

Tawhid and Jihad also released a videotape yesterday of their remaining hostage, Kenneth Bigley, a British contractor, pleading for his country’s leader to release female prisoners.

“To Mr. Blair, my name is Ken Bigley, from Liverpool,” Mr. Bigley said on the video. “I think this is possibly my last chance. I don’t want to die.” He added, ‘Please, please, release the female prisoners that are held in Iraqi prisons. Please help them. I need you to help me Mr. Blair because you are the only per son now on God’s Earth that I can speak to. Please, please help me see my wife, who cannot go on without me.”

In New York, the British foreign minister, Jack Straw, said it appeared there was little hope for Mr. Bigley. “We continue to do everything we can to secure Kenneth Bigley’s safe release, but it would be idle to pretend that there’s a great deal of hope,” he told reporters in New York. “We cannot get into a situation, and I believe the family understand this, where we start bargaining with terrorists and kidnappers,” he said.

On the campaign trail, Mr. Bush said the graphic scenes would not deter America from helping secure Iraq for elections. “You know, these people cannot beat us militarily. And so they use the only tool at their disposal, which is beheadings and death, to try to shake our will,” he said at a stop at King of Prussia, Pa. “These terrorists are hoping to shake the will of the Iraqi people and of the American people. They know what’s on our TV screens. I met yesterday with Prime Minister Allawi… .He said as clearly as he could to me that not only are we making progress, but the Iraqi people want to be free,” the President said.

[Meanwhile, Ayatollah Ali al-Husseini al-Sistani is concerned that elections in Iraq could be delayed, according to a report on the New York Times’ Web site last night. He has even threatened to withdraw his support for the elections unless Shiites receive a greater level of representation, the report said.]