(Reuters) - A blank-check firm backed by veteran Wall Street dealmaker Michael Klein has raised its initial public offering size to $1 billion from $300 million, looking to tap into a roaring investor interest in new offerings. Churchill Capital Corp VII said it was looking to sell 100 million units priced at $10 each, up from its earlier plan of 30 million units, a regulatory filing showed on Monday. (bit.ly/3p01xFJ) Blank-check firms, also known as special purpose acquisition companies (SPAC), typically raise money in an IPO to pursue an acquisition without telling their investors in advance which specific company they will buy. The deal then takes the private company public. Some of Klein-backed blank-check firms have already struck deals. Last year, healthcare services provider MultiPlan signed an $11 billion deal to go public by merging with another entity of Churchill Capital. Apart from Klein, a former Citigroup banker, other high-profile investors such as Chamath Palihapitiya, Alec Gores and Bill Ackman have raised billions of dollars through their SPACs. Citigroup, JP Morgan, Goldman Sachs and BofA Securities are the underwriters for the offering.