Shortly after the meeting Abe announced Japan was giving Laos $1m in development aid for the removal of buried, unexploded bombs.
On Wednesday Japan's deputy cabinet secretary said Tokyo was
pleased with the Laotian decision but denied that Japan had tied the aid to joining the IWC.
"While I believe the decision to become a member of the IWC was the Laotian government's own, we think our efforts to increase global participation in this important committee has won support,'' Hiroshi Suzuki.
The Japanese foreign ministry also rejected suggestions that the aid was linked to Laotian support in the IWC, although an official told the Associated Press that Laos was likely to back Japan's pro-whaling stance.
It is not clear however whether Laos will complete the membership process in time for the Alaska IWC conference.
"To join the IWC in return for receiving aid does not reflect what the Laotian people desire"
Bouasone's visit to Japan was intended to secure investments for Laos - one of South-East Asia's poorest and least developed countries - from the world's second largest economy.
"Japan requested cooperation on preserving traditional culture and we think the reason Laos agreed to join the IWC is to help improve friendly ties with Japan," a the Japanese foreign ministary said.
Environmental group Greenpeace accused Japan of using aid to secure support from friendly developing nations, many in Africa, who have no real whaling concerns.
Commenting on the the Laotian move to join the world whaling body, Junichi Sato, Greenpeace Japan's campaign leader, said there was a chance that just one vote at the IWC "could change things a lot".
"To join the IWC in return for receiving aid does not reflect what the Laotian people desire," he said.
"To have Laos join an international meeting through these obscure means is very bad for both Japan and Laos."
This year's IWC meeting is set to again pit Japan against anti-whaling nations led by Australia, Britain, New Zealand and the United States.
At the last session in the Caribbean, pro-whaling nations won a razor-thin 33-32 victory, passing a symbolic resolution saying the whaling moratorium was no longer necessary but not gathering enough votes to overturn it.