TOKYO (Reuters) - Japanese big manufacturers' sentiment improved in the three months to September for a third straight quarter, the central bank's "tankan" survey showed, cementing the case for Prime Minister Shinzo Abe to proceed with a planned sales tax hike next year.

COMMENTARY:

MASAMICHI ADACHI, SENIOR ECONOMIST, JPMORGAN, TOKYO

"As you know, the headline numbers are probably a bit better than expected and the details are still constructive.

"We see some signs of cautiousness, like a slight downward revision in the capex plan and so on.

"Still, as a whole, the assessment on excess capacity or a shortage of labor suggests the output gap is getting smaller.

"This is very constructive in terms of the assessment of the current economic situation. There is no reason that Prime Minister Abe should stop raising the (sales) tax."

YASUO YAMAMOTO, SENIOR ECONOMIST, MIZUHO RESEARCH INSTITUTE, TOKYO

"Japan's economy is on track, and the tankan has shown broad-based improvement in sentiment.

"Manufacturers had been lagging the overall economy, but the tankan shows improvements in this sector are starting to catch up due to exports and a weak yen.

"The government can go ahead and raise the sales tax as the economy is clearly recovering."

LINK:

For full table, click on the BOJ's website:

http://www.boj.or.jp/en/statistics/tk/gaiyo/2011/tka1309.pdf

(Reporting by Leika Kihara, Dominic Lau and Stanley White; Editing by Chris Gallagher and Edmund Klamann)