Visiting Pakistani President Asif Ali Zardari said he was frustrated that his country wasn't getting the same nuclear benefits as India, Japan's newspaper The Mainichi Daily News reports.
The United States, France and Russia, seeking stronger economic ties with India, have signed nuclear agreements with New Delhi but only after it said it would halt nuclear weapons testing, the report adds.
Neither of the nuclear-armed foes, however, has signed international treaties regarding nuclear weapons.
Islamabad, the report said, is frustrated with what it sees as favoritism toward India. The government there was criticized, however, after it emerged that Pakistani nuclear scientist Abdul Qadeer Kahn gave North Korea information on nuclear weapons technology.
Concerns were raised, meanwhile, over what the report described as Pakistan's purchase of nuclear reactors from China.
"Compared to India, there are certainly more concerns about proliferation," the Japanese Ministry of Foreign Affairs was quoted as saying.