As Prime Minister Narendra Modi left for Japan on a three - day trip on Thursday, China said it expected both countries to respect its "legitimate" concerns.
"We have no problem over the developing normal relations between our neighbours.
We hope that they can respect the legitimate concerns of neighbours, " Foreign Ministry spokesperson Lu Kang said.
China is wary of India and Japan issuing a joint statement on the South China Sea asking Beijing to adhere to the UN - court ruling which rejected Beijing's rights over the disputed waters.
In an oped on Wednesday, the Chinese media warned India of suffering great losses in bilateral trade if it joined Japan in asking Beijing to respect the ruling by an international tribunal.
"India should beware of the possibility that by becoming embroiled in the disputes, it might end up being a pawn of the US and suffer great losses, especially in terms of business and trade, from China, " an oped article in state - run Global Times said.
Lu refused to comment over the arms deal between India and Japan.
In September, China reacted angrily to a report about Japan reducing the price of US - 2 amphibious aircraft, calling it "shameless".
India and Japan may sign a civil nuclear deal and are likely to discuss other important issues.