Japan escalated on Friday its warning to markets against testing the yen's upside further, with the finance ministry signaling that Tokyo may not wait for too long with action if the currency keeps climbing.

In his strongest threat of intervention so far, Finance Minister Yoshihiko Noda said that the yen was rising too much and deviating from Japan's economic fundamentals.

Our stance is clear. We will take decisive action against excessive exchange rate volatility, Noda told parliament.

I'd like to carefully examine how long we can leave current (exchange-rate) moves unattended.

Noda said he hoped to take appropriate action, in cooperation with the Bank of Japan, to address the currency's rise that was hurting exporters and threatening Japan's recovery from damage wrought by the March 11 earthquake and tsunami.

Data released on Friday showed factory output rose further in June and manufacturers expected more gains in July and August that would bring production close to pre-quake levels, but economists said the yen's rise was clouding the outlook.

Policymakers' repeated verbal warnings have not prevented the dollar from sliding toward the record low of 76.25 yen hit in March on growing fears of a U.S. debt default or credit downgrade. It did not move much on Noda's latest warnings and hovered around 77.81.

A senior BOJ official said the central bank was focusing on how recent yen rises could affect a still fragile economic recovery, suggesting its readiness to ease monetary policy further as early as next week if yen climbs further.

SOLO ACTION

Markets rule out a repeat of the co-ordinated intervention that the Group of Seven carried out in the aftermath of the devastating earthquake in March, but some see solo action by Tokyo as a possibility.

Japanese policymakers, alarmed at the persistent nature of yen rises amid a broad-based dollar weakness, see solo action as an increasingly viable option, although markets are skeptical how long its effect would last.

Noda's verbal warning has escalated slightly, said Michiyoshi Kato, senior vice president at forex sales at Mizuho Corporate Bank.

It's not about dollar/yen levels alone. Authorities are probably also watching stock markets. If the U.S. debt problem triggers risk aversion and pushes the yen up suddenly, and if that increases worries about the impact on Japan's economy, Tokyo may act.

Policymakers hesitant of intervention have pointed to the resilience of the stock market as a sign the damage to the economy has been contained so far.

But the Nikkei average fell below the psychologically important 10,000 mark and business lobbies have started to complain more vocally about the government's inaction over the strong yen. Noda said he was aware of business concerns.

The BOJ feels the yen rise has yet to severely undermine business sentiment but is prepared to ease policy further if the standoff in U.S. debt talks roils global markets.

Japan's economy is just recovering from a big shock after the quake. We need to watch out for the negative impact yen rises could have on the economy through exports, corporate revenues and a worsening of business sentiment, BOJ Executive Director Masayoshi Amamiya told parliament on Friday.

Japan's economy is expected to exit recession and grow moderately in July-September as companies make steady progress restoring supply chains hit by the quake.

(Additional reporting by Tetsushi Kajimoto, Stanley White, Rie Ishiguro and Kaori Kaneko; Editing by Tomasz Janowski)

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