WASHINGTON -- With U.S. troops closing in on Baghdad, America's top military man on Thursday cautioned against euphoria in the war against Iraq and said a lot of tough fighting lay ahead.

Air Force Gen. Richard Myers, Chairman of the U.S. Joint Chiefs of Staff, also said that U.S.-led forces might not be in a hurry to overrun Baghdad if it were cut off and President Saddam Hussein was no longer in control of the rest of Iraq.

U.S. troops reached Baghdad airport, just 12 miles (20-km) from the city center on Thursday, in the first ground attack on the capital in 16 days of war. The U.S. military said 320 Iraqi soldiers had been killed in fighting there.

While the U.S.-led forces have met little real resistance during their swift advance through Iraq from the Kuwaiti border, Baghdad is seen as a more difficult objective.

"My view is that there are still a lot of tough fights ahead," Myers said in an interview with fox news channel. "Nobody should be euphoric that now that we are on the edge of Baghdad this thing is just about over. That's not true." He added: "This is not the time for anybody to take a deep breath and think that we have reached some sort of place where we can now think that it's all downhill. I don't think that at all. I think that it's going to be very tough."

Myers said there was no need to rush into Baghdad with much of the rest of the country already overrun and plans in hand for an interim Iraqi government to take over from Saddam.

"Baghdad becomes less and less important. You have a regime inside that can't communicate with the people. All they can do is hunker down and try to survive," Myers said.

He said that 45 percent of Iraq was now no longer under the control of the government.

Addressing concerns about the difficulties of overcoming final "pockets of resistance" in Baghdad, Myers made clear that he would use guided bombs to attack targets suspected of housing organizations such as the ruling Baath Party, the security forces, the military, and the Iraqi leadership.

"But any notion that you have to have some sort of carpet bombing of Baghdad, that's not going to happen," Myers said.

He said U.s.-led forces had yet to discover any chemical or biological weapons during their advance, although documents and chemical suits had been found. "But I suspect the closer we get to Baghdad, and areas around Baghdad ... I think the likelihood of finding WMD (weapons of mass destruction) is higher," Myers said. (Reuters)