By Alina Selyukh WASHINGTON (Reuters) – Pressure built on the U.S. Federal Communications Commission chairman on Thursday to delay or abandon a plan to relax Internet traffic rules, with more than 50 high-profile venture capitalists and another FCC member the latest to pile on. Prominent investors including Ron Conway of SV Angel, Chris Dixon of Andreessen Horowitz, John Lilly of Greylock Partners, Jason Mendelson of Foundry Group, and dozens of other VCs wrote a joint letter to FCC Chairman Tom Wheeler, himself a former private equity investor, sharing their concerns about the proposed new \”open Internet\” rules. Wheeler has been under fire for proposing rules that would allow content companies to pay broadband providers for faster Internet speeds to deliver their traffic as long as the deals are deemed \”commercially reasonable.\” Ajit Pai, senior Republican commissioner at the five-member FCC, on Thursday said he had \”grave concerns\” about the plan and joined his Democratic colleague Jessica Rosenworcel in calling for a delay of the vote scheduled for May 15.