Matildas head coach Tom Sermanni has resigned to take up the same job with the United States women's national soccer team.Sermanni says the decision to leave the team he's coached for the past eight years is not an easy one, but the opportunity to coach the No.1 team in women's soccer is a challenge he wants to accept."In football, and in life, it's all about timing, and with Australian women's football quite settled at the moment with the national teams and the Westfield W-League, the timing of this challenge to coach the number one women's football team in the world was at the right time for me to accept," Sermanni said in a statement on Wednesday."There is plenty of great talent coming through the Australian women's football system and in the coming years I am confident that Australia will be a world force."Football Federation Australia CEO Ben Buckley said Sermanni would be missed in Australia but wished him all the best in the US."Tom's legacy for women's football in Australia will be felt for many years to come as he has helped transform our women's national team to a very professional and competitive group of players," he said in the statement.During his eight-year tenure Sermanni oversaw Women's World Cup campaigns in 2007 and 2011 where the Matildas made the quarter-finals stage as well as a Women's Asian Cup Championship in 2010.Sermanni, who will replace Pia Sundhage in the US, has previously coached the San Jose CyberRays and New York Power in the WUSA.His final Australian coaching duties will be the East Asian Cup Qualification tournament in Shenzen, China from November 20 to 24.