Russian and U.S. arms control envoys began negotiations on Monday. Their main focus - the extension of the New START nuclear arms control treaty. The accord aims to limit U.S. and Russian nuclear warheads. The current one was agreed in 2010 and expires in February next year. It limits each side to 1,550 deployed nuclear warheads. U.S. President Donald Trump has been insisting that China should also be involved in the discussions, even though the country has no deployed nuclear warheads. China's total nuclear warheads account for only 2 percent of the world tally, while the U.S. and Russia hold over 90 percent of them.