Definition: In this task, you need to generate an appropriate title for the given summary of some paragraph. The generated title must be short and should include the main topic of the given text. Your summary should be less than 20 words long.
Input: US President Donald Trump has stepped up his attack on the UK's ambassador in Washington, Sir Kim Darroch, saying "we will no longer deal with him".

Trump: 'We won't deal with UK ambassador' after leaked emails