Japan will overcome last weekend's slaying of two Foreign Ministry diplomats in northern Iraq and send Self-Defense Forces troops to the country when the time is appropriate, Prime Minister Junichiro Koizumi vowed Tuesday.

In a speech in Tokyo, Koizumi said Japan suffered a tremendous loss when "distinguished diplomats" Katsuhiko Oku and Masamori Inoue were assassinated.

"It is truly regrettable, but our government must overcome the deaths of Mr. Oku and Mr. Inoue and cooperate with the international community to build a democratic government in Iraq," he said.

Koizumi did not touch on when troops would be sent, but devoted almost half of the 50-minute speech on the need to dispatch SDF units to Iraq -- his strongest reference since the ambush stunned the nation.

Repeating his resolve that Japan will not yield to terrorism, Koizumi went on to say the troops must be sent.

"We are being tested not just by our words but by our actions," the prime minister said. "When an appropriate time comes, we must send the SDF troops, increase the number of government workers and also ask the brave civilians to cooperate with us to do this difficult job.

"It is in our national interests to do what we can. If we back down now because it's not safe or because anybody could be a target for terrorists, that means we gave in to terrorists," Koizumi said. "There is no change in our stance that we will make a personnel contribution."

Even though terrorist attacks on the U.S.-led forces are increasing, Koizumi said a withdrawal of U.S. or British troops would bring chaos to the Middle East and directly hurt Japan's interests, including the nation's heavy reliance on Mideast oil.

The prime minister also underscored the importance of the Japan-U.S. alliance as one reason for sending troops.

"Japan's security is not guaranteed by our defense capability alone. Our security is maintained under the Japan-U.S. security alliance," he said, adding that keeping strong ties is critically important for Japan in dealing with North Korea.