The upcoming visit of US President Barack Obama to India is going to be a "defining" one in the bilateral ties, BJP said today while expecting enhancement in cooperation particularly in the defence sector. "The way the whole thing has happened (invite to Obama by Modi), it makes it a very defining visit," BJP General Secretary Ram Madhav said here. He said India and the US can cooperate in many areas but defence will be very important, as he highlighted that there has not been adequate cooperation in this sector. When Obama witnesses the Republic Day parade, he will notice that most of the Indian weaponary is imported from Russia and other nations and "very few" from the US, Madhav said at India Today Global Round table discussion here. Noting that the US has been mostly averse to transferring crucial technologies to India, the BJP leader said this has been a major hindrance in enhancing the defence ties. He recalled that former Prime Minister Atal Bihari Vajpayee had called India and the US "natural allies", paving the way for two countries to deepen their ties in the coming years. Obama's visit would "befit this description", he added. He said the US can be of help as Indian Navy is working to upgrade its strengths after being hit by accidents involving several of its submarines. Sanjay Baru, Media Adviser to the then Prime Minister Manmohan Singh, agreed and said a major turning point in the India-US relations was going to be witnessed.