Talks at which Japan pressed its case for pursuing whaling despite a landmark UN ruling were described as "constructive" Wednesday, as a meeting of scientific experts wrapped up in California.

Japanese experts made their latest submission at a closed-door meeting of the International Whaling Commission (IWC)'s scientific committee, expected to make recommendations later this month.

The controversial issue of Japan's whaling for scientific research came up in plenary session only at the end of a two-week meeting at a San Diego hotel of some 200 of the world's leading whaling experts.

"The substance will not be made public until the report is finalized" and published on June 19, IWC spokeswoman Kate Wilson told AFP, calling the talks "extensive and constructive."

Japan has hunted whales for a few hundred years, but while other leading industrial nations including the United States and Britain once hunted whales, the practice fell out of favor and by the 1980s commercial whaling was banned.

Norway and Iceland ignore the ban, but Japan uses a loophole that allows for so-called "lethal research."

But the International Court of Justice, the top UN legal body, ruled last year that Japan's program of "lethal research whaling," carried out in the Southern Ocean for nearly two decades, was a fig leaf for a commercial hunt.

Tokyo is now trying to convince the IWC there is a genuine need for the research they say is being carried out when they slaughter marine mammals whose meat ends up on the dinner table.

After the March 2014 ruling by the Hague-based ICJ, Japan made an initial submission to IWC experts, but their preliminary response was that Tokyo's case lacked important information -- which it was expected to provide in San Diego.

The committee will decide if the submission is now complete and if it is valid or not, and make a recommendation accordingly to the IWC. Approval would be a boost for Japan's whaling lobby, rejection would be a major setback.

The San Diego talks involved "experts on the full range of relevant issues and with papers/presentations from a wide range of government delegation scientists and invited participants," said Wilson.

The scientific committee's report, which will include a summary of discussions and recommendations from the San Diego meeting, will then be presented at the next full IWC meeting, due in September 2016, she said.

Environmental group Sea Shepherd Conservation Society, which has spent a decade harassing the Japanese harpoon ships during the southern hemisphere summer, said it didn't believe Tokyo will persuade the IWC of its case.

"We are not worried Japan will convince the IWC of its case for justifying whaling for scientific research because there is absolutely no justification in modern times to kill whales," the group said in a statement to AFP.

It added: "All necessary data on whales can be obtained through non-lethal research methods, such as biopsy sampling, satellite tracking, and DNA analysis," it added.

"An expert panel of IWC's scientific committee found that Japan's proposed new whale-killing program lacked scientific merit. Now the entire .. committee is reviewing the plan, but we can't imagine that the outcome will change."

Representatives for the Japanese delegation at the San Diego meeting, which opened on May 19, did not respond to requests for comment.