The United Nations (search) will remain "a high-value" target for attacks in Iraq for the foreseeable future, which will severely limit the number of U.N. staff allowed in the country, Secretary-General Kofi Annan (search) said Friday.

"Security will remain the primary obstacle and constraint," Annan said in a report. "A qualitative improvement of the overall security environment is an essential prerequisite for the success of U.N. efforts in Iraq."

The report came as Annan's new envoy, Ashraf Jehangir Qazi (search) of Pakistan, prepares to take up his post in Baghdad with a small team, giving the United Nations an official presence in Iraq for the first time since October.

The world organization pulled out after a spate of attacks against it, including the Aug. 19, 2003 bombing of its Baghdad headquarters that killed envoy Sergio Vieira de Mello and 21 others.

His report to the Security Council on Friday, covering U.N. activities in Iraq since December, noted that the U.N. security chief has determined the U.N. personnel face high risks.

"For the foreseeable future the United Nations will remain a high-value, high-impact target for attack in Iraq," Annan said.

The U.N. mission in Iraq, which Qazi will head, and U.N. agencies and programs will therefore continue to minimize their presence, he said.

The Security Council has given the United Nations a major political role in helping Iraq's new interim government prepare for two rounds of elections and draft a constitution, and it would also like the world body to be a major player in Iraq's reconstruction.

Whether it can be a significant player without a sizeable presence on the ground remains to be seen.

Despite the security constraints, Annan said, the United Nations has remained "fully engaged in Iraq's political transition process," working from U.N. headquarters in New York, from the region, and in sporadic trips to the country. He praised the U.N.'s local staff in Iraq, and organizations in the country helping to run U.N. programs.

Annan said Qazi's primary task will be to assist the Iraqis in political activities leading to the establishment of a constitutionally elected government by Dec. 31, 2005.

Annan has said he expects Qazi to arrive in Baghdad before a national conference of political, religious and civic leaders gets under way in mid-August. A small U.N. team is already there helping with conference preparations.

But the United Nations is having trouble organizing security in Iraq and transportation.

U.N. officials have asked U.S. Ambassador John Danforth for help in finding aircraft to get six staffers into Baghdad quickly to help the team, and sometime next week to transport Qazi to Baghdad, according to a letter obtained by The Associated Press.

The United Nations has also been trying for nearly two months to find countries to contribute troops for a separate force to protect U.N. staff in Iraq, but Annan said Wednesday that no nation has offered a single soldier.

As a result, he told the Security Council that the United Nations will have to rely on the interim Iraqi government and the U.S.-led multinational force for security.

But Annan made clear that the U.N. mission's main base will remain in Amman, Jordan until security improves significantly.