According to a UN watchdog, Japan's plan to discharge waste water from the Fukushima nuclear plant into the ocean complies with international regulations.
The release will have a "negligible," according to the International Atomic Energy Agency, impact on the environment.
The findings come as Beijing and Seoul oppose Tokyo's plan.
The water that was used to cool nuclear reactors is running out of storage space at the Fukushima facility.
Japan hasn't provided a release date, and a regulator still needs to approve the plan in its entirety.
Three reactors at the Fukushima Daiichi Nuclear Power Plant were flooded in 2011 as a result of a tsunami brought on by a magnitude 9.0 earthquake. Since Chernobyl, it is regarded as the worst nuclear accident in history.
An evacuation zone that still exists around the plant contained more than 150,000 people. The Japanese government has spent trillions of yen on the clean-up, which could take 40 years.
The plant's decommissioning has also begun, but it might take decades to complete.
To meet with Prime Minister Fumio Kishida and present the findings of the UN agency's two-year safety review of Fukushima, IAEA Director Rafael Grossi was in Japan on Tuesday.
The organization declared in May that Tokyo Electric Power (Tepco), the country's nuclear watchdog, had demonstrated its capacity to take "accurate and precise measurements" of the radiation levels in the treated water.
Tepco could give its final approval as soon as this week.
Every day, the plant generates 100 cubic meters of waste water. On-site tanks have a capacity of 1.3 million cubic meters.
With the exception of tritium, a difficult-to-filter hydrogen isotope, most radioactive substances have been removed from the water.
According to Tokyo, the tritium levels in the seawater-treated water that will be discharged into the Pacific Ocean are far below those that are considered safe on a global scale.
Tritium levels in waste water from nuclear power plants around the world frequently exceed those in the Fukushima treated water.
China, on the other hand, has harshly criticized Japan's plan and on Monday urged the IAEA not to support it.
However, due to concerns about food safety, South Koreans have stocked up on sea salt before the water is released.
Despite strict testing requirements for food from the area, fishing communities in Fukushima are concerned that consumers will avoid their catches.
