Japan and Russia are likely to shelve a planned visit by Russian President Vladimir Putin by year-end amid a lack of progress in territorial talks between the two countries, Japanese government sources said Wednesday.

"It will be difficult to realize (the visit). There is not much time left," one of the sources said. Another source said Russia's airstrikes in Syria, which have drawn criticism from the United States and Europe, have also made a visit within the year "tough."

Chief Cabinet Secretary Yoshihide Suga said Tokyo will continue to explore the possibility of a visit by the end of 2015 and "make preparations," as agreed by Putin and Prime Minister Shinzo Abe at their summit last November.