President Dmitry Medvedev and Japanese Prime Minister Taro Aso have agreed on the need for a serious response to last week's nuclear test by North Korea as a UN diplomat said Russia now backs sanctions against the country.

Medvedev and Aso had a telephone conversation about North Korea's nuclear explosion, short-range missile launches and declarations about resumption of its nuclear program, the Kremlin said Saturday.

"The parties shared the view that there is a need to most seriously respond to these steps, representing a challenge to the international security system," it said in a statement.

They said they would coordinate on proposals to be included in a new UN resolution, it added.

At the United Nations, ambassadors from the five permanent veto-wielding Security Council members -- the United States, Russia, China, Britain and France -- and Japan and South Korea met behind closed doors Thursday to discuss initial reactions from their governments to a list of proposals for possible inclusion in the new resolution. A diplomat familiar with the talks, who spoke on condition of anonymity, said there was a clear commitment to go for sanctions in the new resolution and no reluctance from Russia and China. Russia has publicly opposed sanctions.

Russia's UN ambassador, Vitaly Churkin, told reporters after the talks that there was wide agreement on what the resolution should include, but he cautioned that putting the elements together and getting agreement would take time because there were many suggestions.

"It would maybe take 10 resolutions to incorporate them all," he said.

Meanwhile, Konstantin Pulikovsky, a former Kremlin envoy who wrote a book about a cross-country train trip with North Korean leader Kim Jong Il, said he believes that Pyongyang will continue its defiance of the United States and the West.

Pulikovsky said North Korea's ambassador recently told him that Pyongyang would "strongly resist dictates from the United States," Interfax reported. "I think all recent actions taken by North Korea are connected with this position, not with the deterioration of the North Korean leader's health," he said Friday. Pulikovsky is a former presidential envoy to the Far Eastern Federal District who accompanied Kim when he took his train trip across Russia in 2001. (AP, Reuters, MT)