Half of the weapons and equipment used by the Indian Air Force are obsolete and need urgent replacement, a top Indian defence official has said. Air Chief Marshal P.V. Naik, pointing to investment by the government in defence, said half of the existing fighter jets, radars, transport aircraft and air defence weapons will be upgraded by 2014-15. The country is reportedly negotiating a 3.5-billion-dollar aircraft defence deal with the United States that will be signed in November when President Barack Obama visits the Indian capital. Naik said the air force was also likely to agree a 25-billion-dollar defence deal with Russia by 2010 to buy advanced stealth fifth-generation fighter aircraft. Around 50 per cent of our equipment is obsolete and needs to be replaced, Naik told reporters on Monday, in comments reported by local media. Ten years ago we had no money for modernisation. This caused some delays. Subsequent planning will fructify by 2014-15, he said. India's air force is just a third of the size of rival China's and far short of what is needed to meet the security challenges facing the country, he said. In February, New Delhi announced a 32-billion-dollar defence budget, a four per cent increase on 2009, when spending was hiked by a quarter. The Indian Air Force has also contracted 18 Spyder low-level quick reaction missile systems from Israel and is jointly developing a medium-range surface-to-air missile system with them. The US agreement will see the Indian air force buy 10 C-17 Globemaster transport aircraft, which are expected to replace the ageing fleet of Russian Ilyushin IL-76, India's The Economic Times newspaper reported recently.