The top U.N. envoy to Afghanistan (search) warned Tuesday that ethnic strife and increased activity by Taliban and rebel forces were threatening the peace process and he called for strengthening Afghan security forces nationwide.

"The process as a whole is challenged by the deterioration in the security environment," U.N. envoy Lakhdar Brahimi told the Security Council.

The security problems, he said, cast "a long shadow over the whole peace process and indeed, over the whole future of Afghanistan."

A U.S.-led coalition expelled the former Taliban government in 2001 and helped engineer President Hamid Karzai's (search) rise to power soon after.

Brahimi noted progress in implementing an agreement reached in December 2001 in Bonn, Germany, that set up the post-Taliban administration and gave the country until this fall to come up with a constitutional framework.

But he said the peace process was jeopardized by daily harassment and intimidation of regular Afghans, fighting between ethnic groups and factional leaders, and a recent surge in attacks blamed on Taliban (search) fugitives and renegade rebel ally Gulbuddin Hekmatyar.

"There are now almost daily attacks by elements hostile to the central government and those who support it," Brahimi said. "Clearly the ultimate solution to such problems lies in creating Afghan security forces capable of ensuring peace."

Brahimi said he was encouraged by the development of a new national army and a national police service. The United States is leading efforts to create an army, and Germany is training a police force.

At present an international peacekeeping force of 4,000 soldiers patrols only Kabul.

Brahimi also noted "worrying reports of hostile elements crossing into Afghanistan over the eastern and Southern borders," and he welcomed efforts by Pakistan to address the problem.

In Kabul, dozens of Afghans demonstrated Tuesday, complaining that the government and the United States haven't done enough to rebuild the country or provide jobs and security.

Demonstrations are rare in Afghanistan, a conservative Islamic nation, and the protest drew a crowd of several hundred onlookers.

The United States has been one of the government's biggest financial and military backers. About 8,500 American troops are still in the country hunting down Taliban rebels and their allies.

The protesters drew a mixture of cheers, jeers and laughter from bystanders.