PRIME Minister Mr Li Peng is undergoing treatment for a bad cold and resting, Foreign Ministry spokesman Mr Wu Jianmin said yesterday. ''Li Peng has caught a bad cold. He is now receiving treatment and taking a rest. When he is well again we will discuss once again the arrangements for his visit to four central Asian countries and Mongolia,'' Mr Wu said. The spokesman gave no other details, nor did he indicate whether the premier was being treated in hospital. Mr Li, 65, cancelled on Monday a scheduled meeting in Beijing with Philippine President Mr Fidel Ramos. The Foreign Ministry announced then he had a chill. He was to have left Beijing on Wednesday for a 12-day trip to Kazakhstan, Kirgyzstan, Turkmenistan, Uzbekistan and Mongolia.