UPDATE 2-Soccer-Holders Japan power into Asian Cup quarters

(writes through)

By Alastair Himmer

HANOI, July 16 (Reuters) - Holders Japan stormed into the Asian Cup quarter-finals with a clinical 4-1 demolition of co-hosts Vietnam on Monday.

But Vietnam, appearing in the tournament for the first time in 47 years, joined Japan in the last eight after Qatar lost 2-1 to United Arab Emirates in the other Group B game.

"I'm still not satisfied," Japan coach Ivica Osim told reporters. "If I was satisfied then I might as well just quit as coach."

Japan's reward for finishing top of their group is a grudge quarter-final against Australia, who avoided an early exit with a 4-0 win over Thailand in Bangkok later on Monday.

A Keita Suzuki own goal put Vietnam ahead after just seven minutes and triggered riotous celebrations among a crowd of 40,000, but it took Japan just five minutes to restore normal service.

Celtic midfielder Shunsuke Nakamura found space on the left to float over a perfect cross for Seiichiro Maki, who had the simple task of chesting the ball into an open goal.

Yasuhito Endo put Japan ahead just after the half hour, rifling a free kick into the top corner from the edge of the box to briefly silence Vietnam's trumpet-blowing fans.