• Cable extends north to threaten 1.3274 as USD falls vs yen on Mimura

• Japan's top FX diplomat urges markets to heed "very clear" warning on yen

• 1.3274 is a former support point (July 28 low). 1.3225 was Asia low

• Resistance levels beyond 1.3274 include 1.3300 and 1.3322 (Sept 22 low)

• CFTC data: net GBP short rose 40% to 82,568 contracts in week to Sept 22

• 82,568 contracts is largest net GBP short position since early July

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(Robert Howard is a Reuters market analyst. The views expressed are his own)