LONDON (Reuters) - Major U.S. cryptocurrency exchange Coinbase said on Wednesday its retail and professional-focused platforms were hit by connection problems and network congestion, as bitcoin smashed through $20,000 to its highest level ever. California-based Coinbase said on its website at 15:41 GMT it had “implemented a fix” to address “congestion issues” on its retail platform Coinbase.com and was monitoring the situation. Network congestion was also delaying the sending of ethereum - the second biggest cryptocurrency after bitcoin, and related tokens, it said. Its Coinbase Pro platform was also hit by the network congestion problems, it said. Bitcoin earlier soared to $20,800, its highest ever, amid increased institutional and corporate interest. It has gained more than 170% this year as larger investors seek it for its purported resistance to inflation. Ethereum, which often moves in tandem with bitcoin, also jumped more than 6%. Last month Coinbase was hit by tech problems during a sharp correction for bitcoin, with users reporting difficulty trading.