The U.S.-led offensive against Iraq has entered a new phase, with allied forces advancing into Iraq from northern Kuwait. But coalition forces also suffered their first casualties, when a helicopter carrying British and American personnel crashed in the northern Kuwaiti desert.

Allied forces have stormed across the Kuwait-Iraq border, and officials at the U.S. Central Command say they are encountering minimal resistance, as they move into southern Iraq.

A coalition official says it has been easy going so far for allied troops, but he expects that resistance will become greater, as U.S. forces get closer to Baghdad.

An armored reconnaissance unit, the 7th U.S. Cavalry, is racing northward across the Iraqi desert, spearheading a move by the 3rd Infantry Division up the Euphrates Valley toward Baghdad.

Meanwhile, a joint expeditionary force made up of U.S. marines and British forces is heading toward Basra, Iraq's second city. From there they intend to move up the Tigris Valley toward the capital.

As the Pentagon in Washington expressed satisfaction with the early stages of the war, at least 12 U.S. marines and British commandos were killed, when their helicopter crashed in northern Kuwait. They were the first allied casualties since military action against Iraq began early Thursday. Officials say they do not believe the crash was the result of hostile action.

A spokesman for British forces at coalition headquarters in Qatar, Flight Lieutenant Peter Darling, said the cause of the crash is under investigation. "These were pretty unpleasant winds [Thursday], and also some during that evening, but it doesn't take that much when you're in a helicopter to start doing some damage," he said.

The ground assault followed a day of Iraqi rocket attacks against U.S. units massed along the Kuwaiti border.

VOA correspondent Alysha Ryu is with a U.S. army helicopter unit in northern Kuwait that is providing support to the columns of coalition forces that have crossed the border into Iraq. In a satellite phone conversation with VOA senior editor Al Pessin in London, she described the scene at her base camp as ground troops went into action.

Pessin: "Alysha, what has been happening during the night and early morning there, where you are with U.S. troops in northern Kuwait?"
Ryu: "We had an evening that started out with some artillery barrages, and when I say some, it was quite intense. It was not very long, about an hour or so, but we had 109 millimeter artillery being shot toward the Iraqis on the other side of the border. And then, after that, things quieted down. We didn't have any more Scud alerts that we had during the day."

In Washington, Defense Secretary Donald Rumsfeld called on Iraqi troops to recognize that the days of Saddam Hussein's regime are numbered, and to disobey the orders of the Iraqi leadership. "There is no question but that that regime is not going to be there in the future," he said. "And, at some point, the people of Iraq and the military of Iraq will register that fact. The people will be enormously relieved and liberated, and the military, if they are wise, will refuse to obey orders, and particularly will refuse to obey any orders involving the use of weapons of mass destruction."

The massive aerial bombing campaign that military experts had expected to precede a ground assault has not yet been unleashed. The Wednesday and Thursday nighttime air strikes were aimed at specific targets. U.S. officials say these initial air attacks are designed to attack the Iraqi leadership. The more intensive bombing may come later, if it is needed.