Japan's first military satellite delayed by Tarpaulin mishap.

The launch of Japan's first dedicated military communications satellite will be delayed by two years after a mishap with a blue tarpaulin damaged sensitive antennas during transportation to Europe's Spaceport in French Guiana, two government sources told Reuters.

The mishap has set back plans by Japan's military to unify it's fractured and overburdened communications network, and could hinder efforts to reinforce defences in the East China Sea as Chinese military activity in the region escalates.

"When we need to shift units to the southwest and troops are moving down from the north, we need a stable communications link and this delay could affect that," a senior Defense Ministry official said on condition he wasn't identified because he isn't authorized to talk to the media.

The satellite was damaged in a plane's cargo hold on May 25 after a tarpaulin blocked valves used to equalize its container's internal air pressure as it descended into the thicker atmosphere when landing in French Guiana, according to an internal Japanese government document viewed by Reuters.

The document did not detail who was responsible for the mishap, or whether they suffered any consequences.

The damage will take more than a year to fix, and could force Japan to pay tens of millions of dollars for stop-gap access to commercial communications satellites it currently uses, the sources said.

"We are not yet at the point where we can decide on a new launch window. We want to do it as soon as we can," a spokesman for Japan's defence ministry said.

The satellite is first of three planned X-band satellites that will deliver a unified communications network designed to quadruple the broadband capacity of Japan's Self Defence Forces.

The military needs the X-band system as it reinforces defences along its far-flung southwest island chain that stretches along the southern edge of the East China Sea, almost to Taiwan.

A lack of a common communications platform between Japan's armed forces hampered rescue operations in the wake 2011 earthquake and tsunami that devastated Japan's northeastern seaboard.

Tokyo and Beijing are locked in a territorial dispute in the East China Sea over a group of uninhabited islands known as the Senkaku in Japan and Diaoyu in China. The two countries are also at odds over the exploitation of gas fields that straddle exclusive economic zones claimed by both.

Japan, Washington's main ally in Asia, is now worried that a recent uptick in Chinese military activity in the East China Sea is a sign Beijing wants to extend its military influence from the neighboring South China Sea as it challenges American maritime dominance.

Japan says it has scrambled air force jets to intercept Chinese aircraft in the East China Sea more often this year and also noted an increase in Chinese navy patrols.