* Dollar/yen offers cited at Y82.00 and above
* Soured derivative bets add to dlr selling interest-dealer
* Yen restrained by risk of BoJ intervention
* USD under pressure elsewhere, index near 15-month low
By Masayuki Kitano and Naomi Tajitsu
SINGAPORE/HONG KONG, March 22 (Reuters) - The yen edged higher on Tuesday, and some traders say a massive build-up of offers to sell dollars may test whether Japanese authorities have a line in the sand at 80 for the USD/JPY to launch intervention.
The dollar looked vulnerable on charts following its recent drop below trendline support against a basket of currencies. The euro made the most of the dollar's woes, hovering near its highest in more than four months against the greenback.
Traders said various market players were looking to sell the dollar against the yen on rallies, with selling interest particularly strong starting from 82.00 yen -- the dollar's high against the yen after Friday's joint intervention.
One trader cited dollar offers from investors at 82.00 yen and above, while a customer dealer at a major Japanese bank said the amount of dollar offers around the 82-yen and 83-yen area have increased sharply in the past few days.
The customer dealer said the amount of such dollar offers at his bank had doubled after a bunch of option triggers were taken out last Thursday, when the dollar slid to a post-World War Two record low of 76.25 yen.
That surge in the yen prompted Japan and other Group of Seven industrialised nations to intervene to sell the yen last Friday, and investors are bracing for the possibility of further action if the yen rises again.
"The size (of the offers) is pretty substantial and makes me wonder if it's really alright for one bank to have so much," said the customer dealer for a major Japanese bank in Tokyo.
The same dealer said last week that players including some Japanese importers and smaller banks were left holding unwanted dollar longs or pricey dollar longs after option triggers linked to FX derivatives were struck as the yen soared last Thursday.
Japanese exporters may gradually lower their dollar offers, given market expectations that authorities are likely aiming to prevent the dollar from dropping below 80.00 yen rather than pushing it higher, the customer dealer added.
Yen volatility has eased significantly since late last week, and some analysts said calmer markets in the coming weeks would decrease the need for Tokyo to smooth any appreciation in the Japanese currency, even if the dollar creeps below 80 yen.
"If we get past the end of the financial year (at end-March) and we're still unclear about the marcoeconomic damage from Japan's earthquake and dollar/yen slides even more, beyond a one-month window it will be difficult for the BoJ to do a whole lot more," said Cliff Tan, Asia FX strategist at Societe Generale in Hong Kong.
The dollar dipped slightly against the yen compared to late U.S. trade on Monday and stood at 80.90 yen , near a session low around 80.85 yen.
The yen was broadly higher on the crosses, with the euro dipping 0.2 percent to 115.07 yen .
The yen's surge last week was fuelled in part by speculation that Japanese insurers may repatriate funds from abroad to secure cash for payments to policyholders, in the wake of the massive earthquake and tsunami that struck Japan on March 11.
Market players say such repatriation by insurers has not occurred, and the impact of any such repatriation is unlikely to be large.
The true scale of Friday's joint intervention is not yet clear though market estimates put it around $30-35 billion-worth of yen sales, mostly by the Bank of Japan.
Dollar/yen implied volatility has retreated in the wake of the surge seen after last week's massive yen selling. One-month vol was around 11.0-12.0 percent, steadying from a pullback from around 20 percent on Thursday.
Lower volatility has provided some opportunity to take on long gamma positions, but traders say the market remains short gamma, leaving options dealers vulnerable to a renewed drop in spot dollar/yen.
DXY BELOW TRENDLINE SUPPORT
The euro held steady at $1.4221 , hovering near Monday's peak around $1.4241 on trading platform EBS, its highest since November.
Euro bulls eyed the $1.4283 peak from November, but traders said U.S. funds were looming with offers above that level, which along with chart resistance was capping the euro's upside.
The U.S. currency struggled broadly, keeping the index at 75.567, near a 15-month low of 75.340 hit on Monday. It has broken below 75.631, a low hit after the Federal Reserve announced a second round of quantitative easing in November.
It was also under trend line support off the 2008, 2009 and 2010 lows and threatening the 2009 trough at 74.170, which some analysts said suggested a long-term reversal of a bullish trend.
Traders linked the dollar's weakness in part to expectations the Fed would maintain its super-loose policy for a long time to come, making it safe to borrow in dollars to fund carry trades.
In contrast, officials at the European Central Bank were chorusing the dangers of inflation and seemed intent on raising rates no matter the global uncertainties.
EU leaders also took a step closer to agreeing a new European Stability Mechanism worth 500 billion euros which would be able to directly buy government paper . (Additional reporting by Naomi Tajitsu in Hong Kong)