The leaders of Iraq's emerging new government must not allow "turbulence or incompetence or corruption" to slow or foil progress toward building democracy and defeating the insurgency, Defense Secretary Donald H. Rumsfeld (search) said.

Rumsfeld arrived at the Iraqi capital before sunrise Tuesday aboard an Air Force C-17 cargo plane for his second visit in three months. The visit reflects a desire to push the political and military momentum that he believes has been growing since the Jan. 30 elections for a national assembly.

Rumsfeld was meeting later Tuesday with Interim President Jalal Talabani (search), the Kurdish former rebel leader, and Ibrahim al-Jaafari (search), the Shiite Muslim who was designated interim prime minister last week.

Once al-Jaafari has chosen his cabinet ministers and they are approved by the National Assembly, he and Talabani are to lead Iraq's transition to a constitutionally elected government by December.

En route from Washington, Rumsfeld told reporters he would press the new Iraqi leadership to avoid delays on either the political or security front at a time when U.S. troops are still being killed or wounded and billions of U.S. taxpayer dollars are being invested in rebuilding the country.

"It's important that the new government be attentive to the competence of the people in the ministries and that they avoid unnecessary turbulence," Rumsfeld said.

Some in the Bush administration are concerned that factional maneuvering during the formation of the transitional government could undermine the counterinsurgency effort that is a key to eventually pulling U.S. troops out of Iraq.

"Anything that would delay that or disrupt that as a result of turbulence or incompetence or corruption in government would be unfortunate," Rumsfeld said.

He would not discuss his thinking on how soon the 140,000 U.S. troops based in Iraq could begin leaving.