Planned talks between Prime Minister Taro Aso and Russian President Dmitry Medvedev in London on the sidelines of a two-day financial summit have been abandoned because Aso's trip has been shortened due in part to North Korea's missile threat, Chief Cabinet Secretary Takeo Kawamura said Wednesday.

"We had to cut short the prime minister's trip due to North Korea's planned launch and it has become difficult (to schedule summit talks with Russia)," Kawamura, the top government spokesman, told a news conference.

In the face of rising tensions over the planned launch, Aso has to put priority in London on meetings with neighboring nations, including China and South Korea, Kawamura said.

At their summit in mid-February, Aso and Medvedev agreed to meet again on such occasions as the Group of 20 financial meeting in London and the Group of Eight summit in Italy in July.

Kawamura added that another occasion for bilateral talks with Russia is coming up soon, as Prime Minister Vladimir Putin is scheduled to visit Japan in May.

Aso is slated to return to Japan on Friday evening. North Korea has said it plans to launch a rocket to put a communications satellite into space, which Tokyo believes is a disguised test-firing of a ballistic missile, sometime between Saturday and next Wednesday.