* Asian stock markets : tmsnrt.rs/2zpUAr4 * S&P 500 futures dip, U.S. relief bill agreed * New strain of coronavirus shuts much of UK * Pound skids as Brexit talks drag on with no deal SYDNEY, Dec 21 (Reuters) - Asian stocks faltered on Monday as unease over a new coronavirus strain that was shutting much of the United Kingdom offset news a deal had finally been struck on a long-awaited U.S. stimulus bill. Sterling slid 1.1% to $1.3370 after several European countries closed their borders to the UK as the country entered a tougher lockdown to fight a new strain of coronavirus. Prime Minister Boris Johnson will chair an emergency response meeting on Monday to discuss international travel and the flow of freight in and out of Britain. That combined with the lack of a Brexit deal to cut 1% off FTSE futures, while EUROSTOXX 50 futures shed 1.5%. MSCI’s broadest index of Asia-Pacific shares outside Japan dipped 0.2% after hitting a string of record peaks last week. Japan’s Nikkei reversed early gains to be down 0.6%, off its highest since April 1991. In the United States, Republican U.S. Senate Majority Leader Mitch McConnell said an agreement had been reached by congressional leaders on a roughly $900 billion COVID-19 relief bill. The news saw futures for the S&P 500 jump at first, only to fade to a loss of 0.1% as the session progressed. Analysts at BofA noted a huge $46.4 billion flowed into equities in the latest week, while the outflow from cash was the largest in four months. There were record flows into tech shares and large flows to the consumer sector, healthcare, financials, real estate and value stocks. BofA chief investment strategist Michael Hartnett said a “sell signal” had been triggered for the first time since February as cash levels declined to 4.0% in the latest Global Fund Manager Survey. “Positioning is getting over-extended as policy support and profits are peaking,” he said in a note. “Expectations for higher growth, inflation and lower interest rates have become consensus and investors are positioning for a very rosy scenario of low volatility and high growth.” Another popular trade has been shorting the U.S. dollar and again positioning was looking over-extended by many measures, giving the currency some respite on Monday. “FX markets await final outcomes of a possible Brexit deal and U.S. fiscal package,” said Ned Rumpeltin, European head of FX strategy at TD Securities. “We remain biased to fade any ‘good news’ kneejerk USD-selling on both fronts, however. These factors look fully priced and the short-USD trade appears increasingly crowded.” The dollar index edged up a little to 90.147 and away from last week’s trough of 89.723, which had been the lowest since April 2018. The euro likewise edged back to $1.2210, while the dollar was steady on the yen at 103.33. The dollar also found support from a Nikkei report that Japanese Prime Minister Yoshihide Suga told Finance Ministry officials in November to make sure the dollar did not fall below 100 yen. The general risk-off mood saw gold prices gain 0.8% to $1,895 an ounce. Oil prices ran into profit-taking after notching up seven straight weeks of gains, with travel restrictions in Europe a further blow to demand. U.S. crude fell $1.45 to $47.65 a barrel, while Brent crude futures dropped $1.53 to $50.73.