TOKYO, June 2 (Reuters) - The United States is seeking to secure supplies of TNT in Japan for 155mm artillery shells, as Washington rushes weapons and ammunition to Ukraine for a counteroffensive against Russian forces, two people familiar with the matter told Reuters.

For war-renouncing Japan, any procurement would test its willingness to court controversy to help Kyiv because export rules ban Japanese companies from selling lethal items overseas, such as the howitzer shells that Ukraine fires daily at Russian units occupying its southeastern regions.

Nonetheless, the allies appear to have found a workaround to enable the TNT sale amid global shortages of munitions.

"There is a way for the United States to buy explosives from Japan," one of the people with knowledge of discussions on the matter in Japan told Reuters on the condition of anonymity, citing the issue's sensitivity.

Export restrictions for dual-use products or equipment sold commercially are less stringent than for items with a purely military purpose, which is why the U.S. can buy Panasonic Toughbook laptops for its military.

Tokyo, which hosted U.S. Defense Secretary Lloyd Austin this week, has told the U.S. government it will allow the sale of industrial TNT because the explosive is not a military-use-only product, the other source said.

The U.S. wants to plug a Japanese company into a TNT supply chain to deliver explosives to U.S. army-owned munitions plants that would pack them into 155mm shell cases, the person added.

Japan's Ministry of Trade, Industry and Economy declined to say whether any Japanese company had approached it about exporting TNT. It added in an email that items not subject to military restrictions would be assessed under regular export rules that consider the buyer's intent, including whether their use would impede international security.

The Japanese defence ministry's Acquisition, Technology and Logistics Agency declined to comment.

The U.S. State Department did not directly address questions from Reuters about whether the U.S. planned to buy TNT in Japan but said Washington was working with allies and partners "to provide Ukraine with the support it needs" to defend itself. Japan, it added, "has demonstrated leadership in supporting Ukraine's defense".