On his first visit to Iraq since the fall of Saddam Hussein's regime, Secretary of State Colin Powell (search) said  progress was being made in building a democracy, but terrorists seeping into the region were hampering that goal.

"There are terrorists who are trying to infiltrate into the country for the purpose of disrupting this whole process and we will not let that happen," Powell said Sunday, appearing with Iraq's new foreign minister, Hoshyar Zebari (search).

The secretary praised advances in Iraq's political and economic development since the end of the U.S.-led war. He gave a rough estimate of 100 terrorist infiltrators but said he was confident the American military could handle the problem.

The attacks on American occupying forces have become an almost daily occurrence in Iraq. Another one happened on Sunday when a roadside bomb hit a convoy in the city of Fallujah (search), killing one U.S. soldier and injuring three others, the military said.

Some 155 soldiers have died in Iraq since President Bush declared an end to major combat on May 1. During the heavy fighting before that date, 138 soldiers died.

"There is still a security problem in Baghdad and throughout the country. We know that," Powell said on "FOX News Sunday."

"And this security threat comes from those who do not want to see Saddam Hussein go and those who want to foment trouble here, terrorists who are coming in, as well as remnants of the old regime."

Powell told Fox News he had a long meeting with U.S. military commanders in Iraq about the Saddam loyalists and terrorist threats to security in the country.

"They are confident they can deal with these remnants of the old regime, but it will take time," said Powell. "But they're hard at work on it. With respect to the terrorists coming in, that's a different kind of threat. But they're hard at work on that threat as well."

Powell flew from Kuwait (search) aboard a C-130 transport plane, arriving midmorning in the Iraqi capital. He posed for photographers with about 20 U.S. troops at Baghdad International Airport (search) and then went by helicopter to Baghdad, avoiding a road that has been the scene of occasional sniper attacks.

Powell, who came with little advance notice because of security concerns, held talks with the team of U.S. officials guiding Iraq in the postwar period. He also met with Foreign Minister Zebari.

Zebari, who took office just a week ago, acknowledged that the security environment will influence the pace of progress toward Iraqi self-rule. He expressed hope that by mid-2004, Iraq will have "an elected legitimate government."

Powell has said Iraqis will decide when the transition to self-government is appropriate. He has voiced concern that a premature transfer of power could leave the country in chaos.

Details about the length of Powell's stay in Iraq and his remaining activities were closely held by U.S. officials. But he was expected to visit locations associated with rights abuses under Saddam's rule.

Defense Secretary Donald H. Rumsfeld, on a visit to Iraq a week ago, visited a mass grave site.

Before reaching the Persian Gulf region, Powell spent Saturday in Geneva, where he discussed transition issues with U.N. Security Council colleagues, some of whom are eager for an early transfer of power to Iraqis.

Powell has made no indication of being willing to yield to these demands.

The Associated Press contributed to this report.