Iraq said Thursday it would have been technically impossible for the Iraqi Army to use poison gas against Kurds, as Washington has charged, and indicated Baghdad may not allow a U.N. probe into the issue.

Turkey said it would not agree to a U.N. request to send experts into its country to determine whether Iraq used poison gas against its Kurdish population."If the Kurds are Iraqis, it's an internal issue. So what is the role of the United Nations in this case?" Iraqi Defense Minister Adnan Khairallah told a news conference.

U.N. Secretary-General Javier Perez de Cuellar asked the Iraqi government on Tuesday to let U.N. chemical experts conduct such an investigation in Iraq.

Khairallah said the offensive that drove tens of thousands of Kurds into neighboring Turkey lasted from Aug. 27 to Sept. 5 and cleaned out insurgents from a strip three to 12 miles wide along the border.

"If it (gas) was used as the American media claims, it was technically impossible, particularly in the mountainous area," he said.

The minister said chemical weapons create a heavy gas which would have clung to the valleys and made it impossible for Iraqi troops to enter the area.

"The area does not need to be attacked in such a way," he said.

He said the strip was too narrow to use such weapons, which "should not be used in an area of less than 50 square kilometers (19 square miles)."

Iraqi Foreign Minister Tariq Aziz acknowledged on July 1 that his country had used deadly chemical weapons in its 8-year-old war with Iran, but he claimed the Iranians had used them first.

The United Nations and other international bodies have several times censured Iraq and Iran for using chemical weapons in the conflict.

"The general rule is not to use it," Khairallah said. But "if there is this rule, then each rule has an exception."

Khairallah appeared to mute Iraqi criticism of the United States over last Friday's Senate vote to impose economic sanctions against his country over use of chemical weapons.

The U.N. investigation request, prompted by the United States, Japan, Britain and West Germany, also called for a team of experts to be sent to Turkey, where 60,000 Kurds fleeing Iraqi attacks have been given sanctuary.

In Ankara, a Foreign Ministry spokesman said Turkey wouldn't accept the team.