KYIV (Reuters) -Ukrainian President Volodymyr Zelenskiy said he discussed air defences in a conversation with U.S. President Donald Trump on Friday, and agreed to work on increasing Kyiv's capability to "defend the sky" as Russian attacks escalate. He added in his account on Telegram that he discussed joint defence production, as well as joint purchases and investments with the U.S. leader. Ukraine has been asking Washington to sell it more Patriot missiles and systems that it sees as key to defending its cities from intensifying Russian air strikes.