BEIJING (Reuters) - China and Singapore on Tuesday sought to put recent difficulties in their relationship over Taiwan and the disputed South China Sea behind them as Singapore s Prime Minister Lee Hsien Loong began a trip to Beijing. Singapore is not a claimant to any disputed part of the South China Sea but is home to the biggest port in Southeast Asia, and has made clear its open economy depends on continued free navigation in the area. China is also suspicious of Singapore s good military relations with the United States and self-ruled Taiwan.  Meeting in the Great Hall of the People, Chinese Premier Li Keqiang told Lee that China and Singapore had maintained mutual respect.  Singapore, Li said, is an important member of the Association of Southeast Asian Nations, and next year will be rotating chair of ASEAN.   I trust this will inject new energy into not just China-Singapore relations but also China-ASEAN relations,  he said. China is worried it could face fresh criticism over its actions in the South China Sea when Singapore becomes ASEAN s chair, and is putting pressure on the city-state to make sure that doesn t happen, people familiar with the situation have told Reuters.  Lee said he was grateful for the attention to the bilateral relationship but also for the  opportunity to discuss how to work together in the regional context and with ASEAN.  Singapore hopes it will be able to bring China and ASEAN closer together, Lee added. The visit of Lee so close to the opening of next month s Communist Party Congress demonstrates the maintenance of high level visits between the two countries, said Bai Tian, the vice director of the Asian department at the Chinese Foreign Ministry.   This is an important political signal,  Bai said. Overall development of bilateral ties was fairing well, and both leaders agreed to  strengthen coordination and cooperation on international and regional matters , according to a readout of the meeting provided by the Chinese foreign ministry.  The United States and Singapore announced an enhanced defense relationship in late 2015, which included deployments of long range P-8 surveillance planes out of Singapore - aircraft which frequently track Chinese submarines. Singapore also has close though unofficial ties with self-ruled Taiwan, which Beijing regards as a Chinese province. Tensions between the two countries burst into the open last November when Hong Kong port authorities impounded nine Singaporean armored military vehicles being shipped home from training grounds in Taiwan. Hong Kong released the vehicles earlier this year amid rare open debates in both Singapore and China about a deteriorating relationship. 