Japan and the United States have postponed security talks involving their foreign and defense chiefs planned for mid-July because U.S. Secretary of State Rex Tillerson will not be available around that time, according to a Japanese source.

The postponement of the "two-plus-two" talks comes as Defense Minister Tomomi Inada remains under pressure to resign over her gaffe in a campaign speech that allegedly undermined the political neutrality of the Self-Defense Forces.

With Inada widely expected to be replaced in a Cabinet reshuffle rumored to be held soon, Japan is likely to go into the talks with a new defense minister.

The two governments were making arrangements to hold the first two-plus-two talks during the Trump administration in Washington around July 14.

It would be difficult for Tillerson to be available around that time, the source told reporters Monday.

The meeting would also involve Foreign Minister Fumio Kishida and Defense Secretary Jim Mattis.

The bilateral security dialogue was last held in April 2015.

Inada has been under fire for her remark last week that implied the SDF supported a candidate in Sunday's Tokyo Metropolitan Assembly election. She retracted the remark and apologized, but opposition parties have said the remark was at odds with the SDF's legal requirement to be politically neutral.

The controversy over her remark is seen as a factor that led to the stinging electoral defeat of Prime Minister Shinzo Abe's Liberal Democratic Party. Inada has vowed not to step down over the issue.