The government will probably postpone Cabinet approval of a basic plan to send Self-Defense Forces units to Iraq until after next week's special Diet session, officials said Tuesday.

The government originally hoped to approve the plan Friday during a Cabinet meeting. U.S. Defense Secretary Donald Rumsfeld will arrive in Japan the same day.

"We have not been able to decide on specifics," Chief Cabinet Secretary Yasuo Fukuda told a regular news conference. "If there was no problem, it would be easy to dispatch (SDF units) anywhere (in Iraq). But we have to be careful in settling on a plan because there are (security) problems."

A senior government official also said Friday approval would be "difficult" in view of the security threat. "It will be after Rumsfeld comes," the official said.

The special Diet session, expected to convene Wednesday and last three days, is to elect the speaker of the House of Representatives and officially name the prime minister in the wake of Sunday's general election. Junichiro Koizumi is certain to continue as prime minister since the ruling coalition retained its Lower House majority.

On Monday afternoon, Koizumi had told a news conference that he viewed the solid Lower House majority secured by the ruling bloc in the election as a public vote of confidence in the controversial SDF dispatch.

Yet the ruling parties, in an executive meeting the same day, decided against deliberating the Iraq troop dispatch plan during the special Diet session, apparently to avoid turmoil in the proceedings, as the Democratic Party of Japan opposes the mission.

The DPJ made great gains in Sunday's race, winning 177 seats in the Lower House.

DPJ leader Naoto Kan harshly criticized the latest development.

"This is a serious problem -- by postponing Cabinet approval, the government is not going to let the people know (about the dispatch plan) until after the special session is over to avoid it being deliberated on," Kan said. "We must deliberate in the Diet over whether there really are noncombat areas in Iraq."

Under the special law on Iraqi reconstruction, the SDF units can only be sent to "noncombat" zones.

Although the government still hopes to send the SDF units by the end of the year, the delay in approving the basic plan will inevitably push back the dispatch; it could take a month between the Cabinet's approval of the plan and the actual movement of troops, during which time the Defense Agency will work out the specifics.

Any dispatch must be approved by the Diet within 20 days of the order being issued. But the likely delay in issuing the order means the Diet will not be able to deliberate the matter until its next regular session, in January.