By Elizabeth Howcroft LONDON (Reuters) - BlackRock's plans for a bitcoin fund have helped push the world's largest cryptocurrency to its highest in a year, but rising interest rates and a regulatory crackdown could choke off the rally, analysts and industry insiders say. Bitcoin jumped more than 15% last week, rising above $30,000 for the first time since April, its best week since March, in large part driven by BlackRock filing an application with the U.S. Securities and Exchange Commission to launch an exchange-traded fund (ETF) backed by bitcoin. If approved, a bitcoin ETF from the world's biggest asset manager could attract investors reluctant to buy the high-risk cryptocurrency directly. The industry has been hit by a loss of investor confidence and heightened regulatory scrutiny this year after a series of collapses at major crypto firms in 2022 left investors saddled with losses.