U.S. Defense Secretary Ash Carter may visit Japan early next month as the two countries aim to conclude a pact to narrow the scope of U.S. military base workers provided limited legal immunity under the Status of Forces Agreement (SOFA), according to a Japanese source.

The two countries are trying to arrange the visit to discuss the pact and a number of other security issues before the Jan. 20 inauguration of President-elect Donald Trump, who has been critical of the Japan-U.S. security alliance, the government source said.

Other issues to be discussed include Japan's request to return before the end of the year some of the land used by the U.S. forces for the Northern Training Area in Okinawa Prefecture, the source said.