* Repeats drawbacks of continuing corporate life support
* Upbeat on global economy, Japan's outlook
* Deflation, rising job losses complicate exit timing (Adds BOJ's export, output assessment)
By Leika Kihara
TOKYO, Sept 18 (Reuters) - Bank of Japan Deputy Governor Hirohide Yamaguchi warned on Friday the central bank's buying of company debt risked distorting the market, repeating a signal the bank may reduce support for corporate finance in December.
The remarks came after the BOJ upgraded its assessment of the economy and financial conditions on Thursday, signalling that the country is ready to pull out of crisis mode as it emerges from its deepest postwar recession.
"What to do with these special measures should be decided in line with the degree of improvements in corporate finance and market conditions," Yamaguchi said in a speech at a euromoney forum.
"We need to pay heed to the risk that keeping these steps in place for long could hamper an autonomous recovery in market functions and distort asset distribution," he said, echoing a remark he made on Thursday.
BOJ Governor Masaaki Shirakawa also said on Thursday the central bank's intervention in the corporate finance market was designed to deal with a severe crisis that had now passed, suggesting there was less need for them.
Credit markets have been on the mend thanks in part to the BOJ's measures to ease funding strains, such as buying commercial paper and corporate bonds from banks.
The average issue rate for one-month CP fell to 0.21 percent in August from a peak of 1.34 percent last December.
That has led to a growing feeling within the board that at least some of the measures might be allowed to end without distorting markets when they expire in December.
BOJ board member Miyako Suda, regarded by markets as holding hawkish views on monetary policy, said earlier this month that the bank should not underestimate the drawbacks of keeping corporate finance support in place for too long.
The BOJ's CP buying has pushed interest rates on such debt so low that some issuers have been able to borrow funds more cheaply than the government, raising the possibility of moral hazard.
But record deflation, rising job losses and weak capital spending all look set to cloud the debate on the timing of the BOJ's exit from the corporate finance market.
"Yamaguchi seems to be underscoring again that the BOJ will not keep the special measures for supporting corporate funding for too long, but again this does not clarify whether the bank will phase them out in December as scheduled," said Takeshi Minami, chief economist at Norinchuki Research Institute.
"The big question remains as to whether the BOJ can actually end the measures, since midsized and small firms still face tough credit conditions."
UPBEAT ON OUTLOOK
BOJ officials will scrutinise the bank's quarterly tankan survey on Oct. 1 for clues on whether sentiment and spending are improving at small firms as well as larger ones to help decide when to phase out its unconventional steps.
Central banks around the world have begun debating how and when to phase out emergency steps to contain the damage wrought by the worst global financial crisis in decades. Most are not expected to do so until well into next year. Yamaguchi, seen as close to Shirakawa, repeated that Japan's economic outlook was still highly uncertain with growth still dependent on the effect of government stimulus measures.
But he said a positive business cycle was starting in Japan's economy with exports and output clearly recovering on rising demand for automobiles and electronic parts.
"A pickup in the global economy is expected to continue for some time," he said.
The BOJ upgraded its assessment on the outlook for exports and output, saying in its monthly report for September that they will continue to increase.
Exports and output have bounced back from a steep fall triggered by the global crisis, helping the economy return to growth in the second quarter.
But economists warn that any recovery will be slow and fragile as the effect of government stimulus will fade early next year.
Regardless of whether the BOJ phases out support for corporate finance in December, it is expected to keep interest rates on hold at 0.1 percent at least until 2011. (Editing by Michael Watson)