Japan covers some of the costs of the U.S. bases in the country under an agreement with Washington, and Tokyo wants to tighten the budget supporting the 50,000 U.S. troops here.
The All Japan Garrison Forces Labor Union said it was calling for a 24-hour strike on Friday because the Japanese government has not responded to questions about discussions between different ministries about the issue.
On Nov. 21, the union carried out a one-day strike in response to a proposal the government made last month to cut benefits. The action was the first nationwide strike at U.S. bases in Japan since 1991, according to the union.
The budget cuts being reviewed include a monthly benefit worth 10 percent of each worker's salary and a special benefit of up to US$54 (EUR36) a month, depending on the worker's fluency in English.
A Japanese Defense Ministry spokeswoman said Friday's strike was likely to affect the bases' operations, but declined to speculate on the potential scale of the impact.
The official, who spoke on condition of anonymity citing policy, said she could not comment on any possible effect the strike might have on U.S.-Japan relations.
Japan's government is under pressure to keep its defense spending down, while still supporting the U.S. troop presence and fortifying its own military.
Japan allocated US$1.98 billion (EUR1.34 billion) as the budget for U.S. bases for fiscal year 2007, which ends in March 2008. Japan pays more than any other country that hosts U.S. troops.
Most of the strikers work in restaurants on the bases, or do cleaning and housing maintenance, according to Japan's Kyodo News agency.