* Dollar/yen jumps nearly 1%, traders suspect intervention
* No confirmation, trader says MOF/BOJ may be changing method
* Euro bounces back after early dip
* Major Japanese banks buying dollar/yen
By Hideyuki Sano
TOKYO, Sept 24 (Reuters) - The dollar vaulted above 85.00 yen on Friday on talk that Japanese authorities intervened for the second time this month to stem the yen's creeping gains of the past few days.
The dollar's jump came after it had fallen to 84.26 yen on Thursday, its lowest level since Japan intervened last week, and traders said major Japanese banks were bidding up the dollar.
Japanese officials stayed mum on whether they had intervened. Top currency diplomat Rintaro Tamaki declined to comment, Jiji news agency reported, and the Bank of Japan also had no comment.
Japan intervened for the first time in six years last week, in repeated action that pushed the dollar up from a 15-year low of 82.87 yen and shunted it above 85 yen.
It stayed above 85.00 yen until the Federal Reserve signalled this week that it might take more quantitative easing steps, putting widespread selling pressure on the dollar and casting doubt over how effective solo intervention can be.
"Rather than saying clearly whether they did or not, they may be trying to make market players jittery," said one Japanese brokerage trader, who thought Japan probably did intervene on Friday.
"I think they are probably changing their methods, with the aim of dampening dollar-selling interest," the trader said.
Some dealers speculated that an apparent lack of complaint by President Barack Obama about last week's currency intervention when he met Japanese Prime Minister Naoto Kan late on Thursday was seen as tacit approval by Washington of Japan's action.
The dollar rose as high as 85.40 yen from about 84.55 before the rumour, climbing more than 1 yen from day's low of 84.34 yen. It later subsided to 84.85.
Obama, who urged Chinese premier Wen Jiabao to take more action on the yuan, did not mention currencies when he met Kan, Kyodo news agency reported.
"The dollar could rise to above 85.50 but I doubt it will rise to around 86 yen, as it failed to hit that level when Japan last intervened," said another trader at a Japanese brokerage house.
On the charts, the dollar has resistance at 85.66 yen, its 55-day moving average which has acted like trendline resistance since June.
Some analysts say if Japan's authorities want to succeed in their efforts to drive the yen lower, they will need to be more aggressive and at the very least push prices above that 55-day moving average.
In addition, to force the market to cover longer-term short dollar positions and push it higher, authorities would also have to push the dollar through resistance up at 85.90 and 86.50.
Last week's intervention was estimated at about 2 trillion yen ($23.70 billion), which if confirmed will be a record for a single day's intervention by Japan. In the wake of that action, the dollar rose as high as 85.94 yen.
Some traders said a rumour that Bank of Japan Governor Masaaki Shirakawa might resign also helped the dollar. The BOJ said there was no truth to the rumour.
The greenback has been under pressure due to shrinking yield gaps between the dollar and the yen.
The two-year bond yield spread fell to around 29 basis points, the lowest in nearly two years, as expectations that the Federal Reserve will adopt quantitative easing brought U.S. bond yields closer to Japanese yields.
As the dollar broadly weakened, the euro edged up about 0.2 percent to $1.3341, ticking closer to a five-month high of $1.3441 struck on Wednesday.
It fell briefly on mounting worries over Ireland, but support at around $1.3280 proved solid. ($1=84.37 Yen) (Additional reporting by Charlotte Cooper, Masayuki Kitano and Reuters FX analysts Krishna Kumar in Sydney and Rick Lloyd in Singapore; Editing by Michael Watson)