US President Donald Trump on Monday urged China on Monday to maintain a secure border with North Korea, pressing Beijing ahead of his anticipated meeting with North Korean leader Kim Jong Un next month aimed at denuclearization, Reuters reported.

“China must continue to be strong & tight on the Border of North Korea until a deal is made. The word is that recently the Border has become much more porous and more has been filtering in. I want this to happen, and North Korea to be VERY successful, but only after signing!” Trump tweeted.