Bernard Lagat may be a veteran on the international running circuit but the Kenyan-born American is keen not to dwell on his age as he faces a testing defence of his world indoor 3000m title here. The 37-year-old was born in Kenya and won silver and bronze Olympic medals (1500m in 2000 and 2004) and a world 1500m silver in 2001 for his native country before taking up US citizenship. He went on to capture two golds for the US team in the 1500m and 5000m at the 2007 world outdoor championships in Osaka, Japan, followed by silver and bronze (5000 and 1500m) in Berlin in 2009 and another silver (5000m) in the Daegu worlds last year. \"I have been disproving people for years,\" Lagat vowed ahead of the March 9-11 world indoor championships here, where he will be defending his 3000m title, which he also claimed in 2004 in Budapest when running for Kenya. \"When I go out for training I am still serious,\" he said. The problem Lagat faces is the sheer strength of the field in the 3000m, raced around 15 often chaotic 200-metre laps. The field features the other medallists in the 5000m from the Daegu worlds: Briton Mohammed Farah, who won gold and also claimed silver in the 10,000m in South Korea, and bronze medallist Dejen Gebremeskel of Ethiopia. The fastest times of the year, however, belong to Kenyan pair Augustine Choge and Edwin Soi, who both posted 7min 29.94sec in the German city of Karlsruhe. \"I believe I am in a good shape,\" said Soi, who won bronze in the 5000m at the Beijing Olympics. \"I have had a good season in the run-up to the world indoors. Two wins in Lievin and Bolzano, and that narrow loss to Choge in Karlsruhe, means I am more prepared than I was when I competed in the 2008 world indoors in Valencia, where I finished fourth. \"Bernard Lagat will obviously be the main threat, by virtue of being the defending champion, but still this should be an open race for any of us.\" The Kenyans\' time set in Germany is almost 18sec faster than Lagat\'s when winning the US title. Farah, 28, has also hit some form, setting a new two-mile European record of 8:08.07 in Birmingham, a time only bettered by Kenya\'s Eliud Kipchoge, who is absent from Istanbul. That race left Farah complaining he felt \"heavy\" and \"disappointed\" but Great Britain head coach Charles van Commenee had no doubts about including the Somali-born athlete for the indoors ahead of the London Olympics. \"It\'s quite normal that athletes get beaten,\" Van Commenee said. \"If athletes remain unbeaten for a number of years, the moment they get beaten is coming closer every day, so that\'s out of the way now. \"I\'ve got no concerns whatsoever. It\'s quite healthy as well, five months before the Games, so there\'s no reason to be concerned. \"There\'s this assumption that Mo is unbeatable but that assumption is only in Britain. I don\'t think in Kenya or Ethiopia people will take the same view.\" Completing the long list of main rivals will be Gebremeskel\'s Ethiopian team-mate Yenew Alamirew, who has produced two impressive performances (7:31.23 and 7:33.30) in recent weeks to prove he will also be in the running.