UN Secretary-General Ban Ki-moon commended a joint China-US presidential statement that the world's two major greenhouse gas emitters will sign the ambitious Paris climate agreement in April.The two countries will sign the Paris Agreement on April 22, months after the historic pact on climate change was adopted in December during the 21st session of the Conference of the Parties (COP21) in France, the statement said earlier on Thursday.Ban also welcomed the announcement that both countries will take their respective domestic steps to join the agreement at an early date this year, Xinhua cited a statement released by Ban's spokesperson as saying.Moreover, the UN chief urged other countries to follow suit so that the agreement can come into force as early as possible.Ban is further encouraged that the two countries will push reducing greenhouse gas emissions through international institutions this year, including the upcoming G20 Summit in the Chinese city of Hangzhou.The Paris Agreement sets a target of holding the global average rise in temperature below two degrees Celsius above pre-industrial levels, and preferably below 1.5 degrees.