London, May 5 : Shares in US regional banks are rising in pre-market trading, amid calls for a ban on short-selling to calm the crisis gripping the sector, media reports said. PacWest shares are up 9 per cent in pre-market, a small recovery after tumbling 46 per cent on Thursday, while Western Alliance have gained 12.7 per cent after a 38 per cent tumble and First Horizon, which lost 33 per cent, are up 7 per cent, The Guardian reported. The White House vowed to monitor "short-selling pressures on healthy banks", and the American Bankers Association urged federal regulators to investigate a spate of significant short sales of publicly traded banking equities, it said. In a letter to US Securities and Exchange Commission Chair Gary Gensler, the ABA said it had also observed "extensive social media engagement" about the health of various banks that was out of step with general industry conditions. Short-selling is the practice of borrowing shares, and then selling them, in the hope of buying them back at a cheaper price for a profit. Neil Wilson of Markets.com pointed out that the turmoil has begun at banks who were suffering deposit flight (such as Silicon Valley Bank), but is now spreading to others, The Guardian reported. "The thinking is that the regulators ban short-selling to buy time to come up with some kind of plan to rebuild the industry. "There may need to be a 'whatever it takes' line in the sand moment ?? clearly the US authorities haven't done that ?? it may be that a ban on shorting bank shares forms part of that. Remember this bank stress is just on being the wrong side of rates, we've not even had a recession or full credit cycle." /IANS