PHNOM PENH (Reuters) - Cambodian Prime Minister Hun Sen, facing Western donor pressure over a crackdown on critics ahead of 2018 elections, will seek more aid and investment from China during a visit this week, his aide said on Wednesday. China is already Cambodia s biggest donor and its support has bolstered Hun Sen in the face of criticism of what his opponents say amounts to the destruction of democracy. The aide, Sry Thamrong, said Hun Sen would attend a special summit from Thursday to Sunday held by the ruling Communist Party on a theme espoused by Chinese President Xi Jinping on turning the world for the better and without interference.  The aim of Hun Sen s meetings to discuss aid and investment with Xi and Chinese investors is to create more jobs in Cambodia, he said.  Especially, we need more bridges on the Mekong River, we also need many more roads, trains, sky train,  Sry Thamrong told reporters at the international airport in Phnom Penh, the capital, before the departure.  These are the things we need in the future.   China has supported Cambodia s crackdown, making no criticism of the government, which is one of Beijing s most important allies in Southeast Asia after more than three decades in power.     The supreme court this month banned the opposition Cambodia National Rescue Party (CNRP) at the government s request. That followed the arrest of its leader Kem Sokha for plotting to take power with American help. The United States has stopped election funding ahead of next year s general election and threatened further concrete steps. The European Union has raised a potential threat to Cambodia s duty free access. Washington is working on a review of its ties with Cambodia after the dissolution of the CNRP, William Heidt, the U.S. ambassador to Cambodia said.   That is something we are taking very seriously, having a very serious review of our policies towards Cambodia,  he told broadcaster Voice of America in an interview on Wednesday. 