A short time later, Iraqi authorities shut down an office of the Kurdistan Democratic Solution party in Irbil , an organization that allegedly had close ties to Kurdish guerrillas.

The top U.S. diplomat, Secretary of State Condoleezza Rice, was playing go-between with Turkish and Iraqi officials as escalating tensions along the Turkish-Iraqi border overshadowed an international meeting on Iraq's future. Turkish troops are massed on the border, and world leaders are trying to prevent an assault that could open a new front in the Iraq war.

"Iraq should not be a base for attacks against neighbors," al-Maliki said. "We will cooperate with our neighbors in defeating this threat."

The U.N. chief appealed for dialogue to resolve fears of a Turkish offensive against the rebels.

"The series of incidents along the border between Turkey and Iraq demonstrates the need for continuous engagement to address concerns," U.N. Secretary-General Ban Ki-moon told the delegates. "We recognize Turkey's security concerns."

Rice and her foreign minister counterparts from Iraq and Turkey held a private meeting on the sidelines of the conference. The small session began with stiff smiles and pleasantries before reporters were ushered away.

Earlier, al-Maliki's spokesman had warned that no one can stop Kurdish rebels in Iraq's remote northern border region from attacking Turkey.

"It's not in our capacity" to capture the rebels, Iraqi government spokesman Ali al-Dabbagh said. "It's not even in the capacity of Turkey."

Turkey has sought the closure of the office in Irbil, accusing it of being a front organization for the Kurdistan Workers' Party, or PKK.

But Faeq Goolpie, the head of the Kurdistan Democratic Solution party, told The Associated Press by telephone the organization has no connections with the rebels.

"The authorities in Irbil have closed our office without an explanation. The security forces came to the office and made official lists of the materials and equipment in the office and ordered everyone to leave. No one was arrested," Goolpie said.

Turkey is hosting the Istanbul gathering, which includes about two dozen nations and organizations pledged to support Iraq's U.S.-backed government economically and politically.

The guest list includes Iran and Syria, two nations the United States blames for furthering instability and violence inside Iraq. Rice sat across from Iran's foreign minister at an opening dinner Friday night, but the two had no private meeting - something Iraq and many other Mideast nations had hoped for.