"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 on his plane before arriving in Baghdad on Tuesday on his ninth visit to Iraq since the invasion.
"We have an opportunity to continue to make progress politically, economically. Anything that would delay that or disrupt that as a result of turbulence, or lack of confidence or corruption in government, would be unfortunate," he said.
He also cautioned against delays in the political process, particularly the drafting of a new constitution that is due for completion by mid-August, ahead of elections in December.
After meeting Rumsfeld, new Prime Minister Ibrahim al-Jafari said he hoped for a stable political transition.
"I don't deny there are challenges," said al-Jafari, who heads Dawa, a Shia political party.
Talabani said the new cabinet
would be formed in a week
"I am sure we are going to form very good ministries. All of them are good technocrats. They are very effective from different backgrounds. So, I think we can cooperate, all of us, and face these challenges successfully," he said.
President Jalal Talabani, after meeting Rumsfeld, said: "We need time to form the cabinet, which we hope will be finished before the end of this week."
Noting a legal provision allowing a delay of six months in writing the constitution before the next round of elections, Rumsfeld said the US would oppose such a move.
"If someone wants to hang around waiting for perfection in this business, you are unlikely to find it," he said.
"If someone wants to hang around waiting for perfection in this business, you are unlikely to find it"
US Defence Secretary
Rumsfeld said the US military hoped to cut troop numbers next year as long as Iraqi security forces continue to improve.
"The presence of security forces is not going to be something that is going to go on forever," Rumsfeld said before meeting General George Casey, commander of US forces in Iraq, who said Iraqi forces were improving but not ready to rule yet.
At the conclusion of his Iraq visit, Rumsfeld will travel to Pakistan on Wednesday for talks with President General Pervez Musharraf, a key ally in Bush's so-called war on terrorism, officials said.
Rumsfeld is travelling to several countries on a tour of the region including Afghanistan.
The US has granted major military and economic aid to Pakistan in the past three years, and last month announced it would sell Pakistan US-made F-16 fighter jets, fulfilling a long-standing request by Islamabad.