I don’t understand the meaning of 称日 in the first sentence.
I read the title as something like - Japanese official says that Japan will be Shanghai World Expo’s biggest overseas supporter. (eg will supply a significant amount of tourists during this period).
…the good ol’ days of ri-zhong relations…
The shortened version of Japan (日本) really sounds awkward in this context. Normally shortened versions of country names are only used in words like 日方，日中关系，isolated like this I cannot remember having come across it before. Maybe a character got lost when the text was imported into Lingq.