Nineteen and counting -- Michael Phelps was back on the blocks at the London Aquatics Centre Wednesday, one day after he made history yet again with his record 19th Olympic Games medal. The US superstar, whose perfect eight-gold campaign in Beijing had already given him the most golds of any Olympian, added a new line to his legend as he surpassed Soviet gymnast Larisa Latynina's record of 18 career medals with a silver and a gold on Tuesday night. The feat brought congratulations from around the world, including a tweet from US President Barack Obama. "Congrats to Michael Phelps for breaking the all-time Olympic medal record. You've made your country proud. -bo," the president posted, his initials 'bo' signifying he composed the message personally. "I started scrolling through thousands of mentions and I thought, 'Man, this is a lot of things to look at,'" Phelps said of the response to his achievement. "I just wanted to say thank you to all my friends who sent tweets to me, Obama and (Barcelona star Gerard) Pique the soccer player, there were a bunch of different athletes. "Figures from all over the world were sending things, which was pretty cool." Phelps, whose seven-event London campaign has so far yielded two silvers and Tuesday's 4x200m freestyle relay gold, said he didn't get much down-time before he was back at it in the heats of the 200m medley. "I didn't get much sleep last night, I didn't warm down at all," Phelps said after posting the fourth-fastest time of the morning. "I guess we left the dining hall at 11:30 and got to the room at 12. I don't know when I fell asleep. "This morning didn't feel too comfortable."