Yen jumps briefly as Japan takes on speculators

* Yen rises sharply in thin trade

* Traders suspect follow-up ​to last ⁠week's intervention

* Tokyo buying unlikely to reverse yen weakness - analysts

SINGAPORE, May 4 (Reuters) - A brief jolt higher in the yen on Monday sparked speculation that Japan had again sought to defend its sinking currency, though analysts say pressure is likely to persist ​even ‌as the risk of further official intervention looms.

The yen has languished for weeks near record lows in real terms, with policymakers cautioning that its weakness is stoking inflation and squeezing living costs. Those ⁠warnings appeared to turn into action last week, when sources told Reuters authorities had bought ⁠yen. Money market data pointed to roughly $35 billion in spending behind ​a sudden 3% rally in the currency on Thursday.

Monday's move was more modest, briefly pushing the yen from around 157.2 per dollar to just below 156 before quickly unwinding, leaving it near 157.

Markets viewed the jump as a warning shot to speculators betting against the currency, though its swift reversal underlined how difficult it will be for authorities ​to counter years of ‌decline through intervention alone.

Japan's Ministry of Finance (MOF) was not immediately available for comment on the market moves when contacted by Reuters on a public holiday in Japan.

Finance Minister Satsuki Katayama told reporters in Uzbekistan she had no comment when asked whether authorities had intervened, according to Bloomberg.

"The late move in dollar/yen could reflect either a small, calibrated operation by the authorities or simply market moves amplified by Golden Week's thin liquidity," said Masahiko Loo, senior fixed income strategist at State Street Investment Management.

"Either way, ​the intent appears to be about keeping markets alert rather than deploying maximum firepower," he said, while adding that intervention only "buys time", with rate hikes necessary to really lift ‌it.

HARD FOR INTERVENTION TO REVERSE YEN DECLINE

The yen has been under pressure for years, first from Japan's ultra-low interest rates, then on fears of Prime Minister Sanae Takaichi's plans to borrow and spend to boost growth, and now by ‌its exposure to the global oil shock.

Speculators have leaned hard into that weakness. Net short positions in the yen touched a nearly two-year high last week , the most recent CFTC data showed, with bears emboldened when the Bank of Japan left interest rates on hold a week ago.

It will not be clear until later ​this week, when the figures are next published, whether those bets have retreated or whether investors are capitalising on a slightly stronger yen to open new positions.

"I think a lot of investors will ‌see this as something of a gift," said Ian Samson, a multi-asset portfolio manager at Fidelity International, who had until January held a short yen position, but is currently neutral on the currency.

"Now that you're likely to see those (short) positions having washed out and room for the yen to weaken again...it seems pretty likely that investors would take ⁠this as an opportunity ⁠to bet against the yen again and re-initiate yen carry trades."

To be sure, more speculation may draw further ‌responses from Japan, and Barclays said based on previous experience, persistent short bets tend to draw consecutive intervention.

But analysts point to the global backdrop and see little in the recent moves by Tokyo to ​alter the broader outlook: Japan's interest rates remain ​below inflation, and markets no longer expect U.S. rate cuts this year.

"The intervention does not affect our medium-term yen-bearish ‌view," said analysts at JPMorgan in a client note, who see the dollar/yen rate at 164 at the end of the year.

"For currencies like the JPY - freely traded under a floating exchange-rate regime and with a large market size - it is difficult for FX intervention to halt or reverse a fundamentals-driven trend."