Tokyo and London have decided to postpone their ministerial security talks scheduled for next week, a Japanese government source said Wednesday, due to the U.K. Parliament's continued efforts to end the Brexit impasse.

The fourth "two-plus-two" meeting between the two countries' foreign and defense ministers planned for Monday in Tokyo will be rescheduled by the end of May, the source said.

The U.K. government proposed earlier in the week to postpone the meeting, citing the parliamentary duties of Foreign Secretary Jeremy Hunt and Defense Secretary Gavin Williamson, according to the source.

They are to discuss closer defense cooperation including expanded joint training with Foreign Minister Taro Kono and Defense Minister Takeshi Iwaya.

Japan and the U.K. last held such security talks in December 2017 in London.

With the aim of promoting a "free and open Indo-Pacific" region amid China's growing maritime assertiveness, Japan wants to see the U.K. more deeply committed to the region, according to government sources.

In January, Prime Minister Shinzo Abe and his U.K. counterpart, Theresa May, agreed at their meeting in London to hold the two-plus-two meeting in spring in Tokyo.