* BOJ won't hesitate to buy more JGBs from market -Hirano
* Japan economy may contract this fiscal year on quake damage
* Damage from power shortage, nuclear crisis to last years
* G7 may act on forex again, separate statement unlikely (Adds quotes, details)
By Leika Kihara
TOKYO, April 4 (Reuters) - The Bank of Japan will not hesitate to buy more government bonds from the market if needed to calm investors, as the country's economy may contract this fiscal year due to the earthquake, a former senior BOJ official said.
While the yen is likely to weaken in the medium to long term as the BOJ maintains its ultra-loose monetary policy, the Group of Seven will likely step into the currency market again if the yen spikes at an alarming rate, said Eiji Hirano, who as executive director at the Japanese central bank attended numerous G7 gatherings.
"The yen's move just after the quake was a perfect case for concerted intervention," Hirano told Reuters in an interview on Monday.
"The markets are still unstable. In the event of severe market turmoil, the G7 nations may jointly intervene again."
In their first joint intervention since 2000, the Group of Seven nations sold the yen after it spiked to record highs after the March 11 earthquake, threatening to deal another blow to an export-reliant economy that was just picking up from a lull when the disaster struck.
G7 nations are unlikely to issue a statement on currencies when they gather on the sidelines of an IMF meeting later this month, but will stick to their stance of taking action in currency markets when necessary, said Hirano, who left the BOJ in 2006 but has close ties with central bankers across the globe.
Japan is struggling to contain a nuclear crisis triggered by the quake and subsequent tsunami but also needs to start finding ways to cover the huge cost of disaster relief and keep damage to the fragile economy to a minimum amid the threat of electricity blackouts due to the loss of power plants.
Some lawmakers have called on the BOJ to directly underwrite government bonds to help pay for disaster relief, although key cabinet ministers and senior ruling party lawmakers have dismissed the idea as unlikely and inappropriate.
Hirano toed the BOJ's official line, saying that for the central bank to print money to directly finance government debt would further undermine market confidence in Japan's fiscal discipline and could backfire by triggering sharp rises in bond yields.
But he said there was more the BOJ could do, such as further expanding its asset buying programme or buying more government bonds from the market.
"The BOJ already buys government bonds from the market. I think it won't hesitate to buy more government bonds if it feels doing so would help keep markets stable," Hirano said.
The BOJ is expected to revise down its assessment of the economy at a meeting ending on Thursday and to discuss launching a new scheme to offer quake-hit financial institutions one-year loans at an interest rate of 0.1 percent, sources say. [ID:nL3E7F105M]
The BOJ board may also consider easing monetary policy further if it is convinced that the disaster could sharply delay the economy's return to a moderate recovery, although the dominant market view is for the BOJ to stand pat at least until the following review, due on April 28.
The government last month estimated direct damage from the quake and tsunami at as much as $310 billion, making it the world's costliest natural disaster.
But the estimate does not take into account the effect of power blackouts on factory output and business sentiment, which Hirano says could weigh on Japan's economy for several years and nudge it into a contraction in the financial year that began on April 1.
"The biggest problem is shortage of power supply. Factory output will slump in the near term. But the long-term pain will be felt more by the service sector, which consumes a lot of electricity," said Hirano, who is now executive vice president of Toyota Financial Services, the financial arm of Toyota Motor Corp . (Additional reporting by Yuko Yoshikawa; Editing by Edmund Klamann and Michael Watson)