Japan will launch a tender for fighter jets as soon as mid-July, the Ministry of Defence said, in a deal seen worth up to $40 billion as Tokyo seeks to bolster its air defenses amid creeping tension with China over disputed maritime borders, Reuters reports.

In one of the biggest fighter jet contracts up for grabs in years, a ministry spokesman said Japan will contact foreign and domestic defense contractors soon after a July 5 deadline for expressions of interest in the tender for about 100 warplanes.

People familiar with the matter said U.S. firms Boeing Co and Lockheed Martin Corp have been invited to take part in the project, dubbed the F-3 fighter jet program, alongside Japan's Mitsubishi Heavy Industries Ltd (MHI), the prime domestic contractor.

A final decision is likely in summer 2018, the people said, with deployment due at the end of the 2020s at the earliest. They declined to be identified because the matter was confidential.

With a value seen by these people at up to $40 billion, the F-3 program will dwarf most recent fighter jet deals in value, likely attracting global contractor interest. But analysts say Japan's preference for an aircraft that can operate closely with the U.S. military, given close Washington-Tokyo ties, makes a non-U.S. option a long-shot.

The project launch comes as Japan seeks a plane to maintain air superiority over China, now asserting itself in regional maritime disputes. China's warplanes still lag aircraft used by the U.S. and its allies, but Beijing has been building its capability, military experts say, fuelling Japan's more muscular security agenda under Prime Minister Shinzo Abe.

Touted as a replacement for existing Mitsubishi F-2 multi-role fighter jets, the new home-grown aircraft will operate alongside Lockheed F-35 fighters that Japan has on order, as well as Boeing F-15Js jets that it is upgrading. A spokeswoman for MHI said the company doesn't comment on individual projects.