HONG KONG - Asian markets suffered a sell-off Wednesday after a US Federal Reserve head said the central bank’s huge stimulus plan unveiled this month might not boost the economy as much as hoped.Eurozone debt fears were also fuelled after a European Central Bank (ECB) official said it could not restructure Greece’s debt with the regional lender, while tensions between China and Japan continued to weigh on markets. Tokyo tumbled 2.03 percent, or 184.84 points, to 8,906.70, Sydney shed 0.26 percent, or 11.3 points, to 4,361.6 and Seoul slipped 0.55 percent, or 10.97 points, to 1,980.44.Hong Kong fell 0.83 percent, or 170.95 points, to 20,527.73 and Shanghai lost 1.24 percent, or 25.12 points, to end at 2,004.17, a 44-month low. The global excitement stoked over the past month following stimulus announcements in the US, Japan and Europe was given a jolt after the head of the Fed’s Philadelphia branch questioned the impact of the US bank’s move.Charles Plosser said he was doubtful the unlimited bond-buying programme unleashed by the Fed would charge up the US economy, and warned that the Fed could lose credibility because of it.IG Markets said in a report: “Many traders feel central bank stimulus is merely a sticking plaster for a broken leg and that much more needs to be done to send the global economy safely on the road to recovery.”His comments reversed an early Wall Street rally that had been fuelled by upbeat data on consumer confidence and house prices. By the end of trade the Dow fell 0.75 percent, the S&P 500 lost 1.05 percent and the Nasdaq shed 1.36 percent.In Europe, worries over Greece were back in focus as ECB executive board member Joerg Asmussen dismissed an idea raised by Athens that Greek bonds at the bank could be rolled over to bridge a fresh financing gap in the country.He told Germany’s Die Welt daily such a move would be “forbidden monetary financing”.His comments came after Greek deputy finance minister Christos Staikouras last week told parliament the maturity of Athens’ bonds owned by the ECB and worth around 28 billion euros could be extended by mutual agreement.Greece is struggling to apply a fiscal overhaul mandated by the ECB, European Union and International Monetary Fund in return for a new tranche of bailout cash. Dealers are on edge as they await a decision from Spain on asking for a bailout.Madrid is expected Thursday to adopt a 2013 austerity budget that could be a precursor to a full-blown bailout, but Prime Minister Mariano Rajoy has refused to ask until he knows what the conditions will be.A request for cash would allow the ECB to then step in and begin buying sovereign bonds, which would ease the country’s crippling debt woes.On currency markets the euro bought $1.2873 and 99.91 yen in European trade Wednesday against $1.2902 and 100.36 yen in New York late Tuesday.The dollar was at 77.62 yen against 77.79 yen. In Tokyo and Shanghai, shares were also under pressure because of the ongoing diplomatic spat between the two countries over a group of islands in the East China Sea.The row, which has seen violent protests across China, has hit China-linked Japanese firms. Toyota and Nissan said Wednesday they would cut production in the country because demand for their cars had tumbled.Toyota Motor ended 2.66 percent lower and Nissan Motor lost 2.63 percent.“In the foreground there seems to be geopolitical risk between Tokyo and Beijing,” Matthew Sherwood, head of investment market research at Perpetual Investments in Sydney, told Dow Jones Newswires.“People are still quite worried about Japan’s export-based economy.” Oil prices weakened, with New York’s main contract, light sweet crude for delivery in November, sinking 46 cents to $90.91 a barrel in the afternoon and Brent North sea crude for November delivery shedding 59 cents to $109.86.Gold was at $1,763.60 at 1050 GMT compared with $1,764.30 on Tuesday.In other markets:— Singapore closed 0.67 percent, or 20.45 points, lower at 3,046.68.SingTel tumbled 3.90 percent to Sg$3.20 after state-linked investment firm Temasek Holdings said it will cut its stake in the local telecom giant to 51.9 percent from 54.4 percent. DBS Bank was off 0.83 percent to Sg$14.26.— Taipei fell 0.83 percent, or 64.50 points, to 7,669.63.TSMC rose 0.58 percent to Tw$86.4 while Hon Hai Precision lost 3.53 percent to Tw$90.2.— Manila closed 0.61 percent lower, losing 32.54 points to 5,292.63.Alliance Global Group slipped 1.45 percent to 13.60 pesos but Bloomberry Resorts rose 4.01 percent to 10.90 pesos.— Wellington lost 0.42 percent, or 15.99 points, to 3,809.32.Fletcher Building fell 3.0 percent to NZ$6.85, Sky City slid 3.6 percent to NZ$3.78 and Telecom was up 0.2 percent at NZ$2.40.— Jakarta fell 1.11 percent, or 46.72 points, to 4,180.16.Coal company Bumi Resources fell 2.9 percent to 670 rupiah, its rival Indika slid 1.9 percent to 1,590 rupiah and car maker Astra International lost 2.7 percent to 7,200 rupiah.— Kuala Lumpur was flat, edging up 0.72 points to 1,619.30.— Bangkok eased 1.00 percent, or 12.91 points, to 1,274.50.— Mumbai slid 0.33 percent, or 62.24 points, to 18,632.17.India’s biggest mobile phone firm Bharti Airtel fell 3.93 percent to 265.2 rupees on profit-taking after a sharp run-up in prices recently.Cash-strapped Kingfisher Airlines rose 8.65 percent to 15.7 rupees after promoter-billionaire Vijay Mallya said talks were on with foreign carriers to sell a stake in his ailing airline.