Defence Secretary Gavin Williamson is believed to have asked Prime Minister Theresa May for 400 more soldiers to be sent to help the fight against the Taliban. 600 British soldiers are already training Afghan forces. LONDON: Britain could substantially boost its troop numbers in Afghanistan following demands from US President Donald Trump that NATO members "pay their fair share", The Times reported Friday. Defence Secretary Gavin Williamson is believed to have asked Prime Minister Theresa May for 400 more soldiers to be sent to help the fight against the Taliban, adding to the 600 already training Afghan forces. Trump announced last year that the US would send an additional 3,500 troops to secure areas that had fallen under Taliban control and has frequently warned that members need to fulfil their commitments to NATO spending. "Twenty-three of the 28 member nations are still not paying what they should be paying and what they"re supposed to be paying for their defence," Trump said at NATO"s headquarters in Brussels last year. May is due to make an announcement at a NATO summit in July, where it is anticipated Trump may turn the screw even further. Britain"s Ministry of Defence (MoD) said it remained "committed to NATO"s ...mission, in which we play an important role, and keep our contribution under constant review." Richard Barrons, a former commander of Joint Forces Command, said Britain needed to acknowledge that challenges still remained in Afghanistan. "When we left it was not the case that the Afghan national army and the air force were strong enough to tip the balance against the Taliban and that now has to be reset," he told the BBC Radio 4 Today programme.