The Japanese government is "almost certain" a body earlier believed to belong to a Japanese hostage held in Iraq is not that of the captive, officials said Saturday.

The government had said a body found in central Iraq resembled that of hostage Shosei Koda (search), 24, and that it was being sent to medical experts for identification.

A Japanese doctor and officials in Kuwait examined it but found the body's characteristics differed from Koda's, said Chief Cabinet Secretary Hiroyuki Hosoda.

"It is almost certain the body is not Mr. Koda," Hosoda said. "We are now collecting more information and turning our full efforts toward rescuing Mr. Koda."

Foreign Ministry spokesman Hatsuhisa Takashima (search) told a news conference there were several discrepancies, including that the body was dressed in Middle Eastern clothing; the face, though mutilated, had traces of a beard; and the person seemed to be about 50 years old, was overweight, and had a different dental structure.

The discovery came a day after a deadline set by militants who threatened to behead Koda unless Japan withdrew its forces from Iraq — a demand Japan rejected.

Japan had notified Koda's family a body had been found. The government had earlier begun asking for Koda's fingerprints and other medical records to assist the identification.

In a video posted on a militant Web site Tuesday, an al-Qaida-linked group led by Abu Musab al-Zarqawi vowed to behead Koda within 48 hours unless Japan withdrew its troops from Iraq. The captors have not come forward with a statement since then.

Elsewhere, a Sudanese interpreter working for a U.S. contractor appeared on an Arabic television station Saturday, saying he was kidnapped by a group demanding that his firm leave Iraq.

Noureddin Zakaria of Khartoum, who was surrounded by armed men, said on a tape broadcast by Al-Arabiya television that he worked for the Titan Corp., and was kidnapped during a military operation in the insurgent stronghold of Ramadi, 70 miles west of Baghdad.

Titan Corp., based in San Diego, Calif., is the largest provider of translators to the U.S. government.

"I hope and call on the company to stop its operations in Iraq to guarantee my release," Zakaria said on the tape.

Behind him was a green banner with the name "The National Islamic Resistance, the 1920 Revolution Brigades." The group has promised to "liberate" Iraqi territory from foreign occupation and has carried out attacks mostly in the area west of Baghdad.

The 1920 Revolution refers to the uprising against British military occupation, which historians consider the birth of Iraqi nationalism.

Koda, who left Japan in January for a yearlong trip starting in New Zealand, had told people he met traveling that he wanted to go to Iraq to see the country.

The crisis comes as support ratings for Koizumi's government have been sliding. Many Japanese oppose his dispatch of about 500 ground troops to southern Iraq, saying the mission is too dangerous and violates Japan's pacifist constitution.

A poll by the Asahi newspaper taken before Koda's kidnapping and published Tuesday showed 63 percent of voters want the military to return by the end of the year.