SEOUL North Korea and Russia have signed a trade memorandum and pledged to strengthen economic ties, Pyongyang state media reported late on Tuesday following a visit by President Vladimir Putin's representative to the Russian far east.

The North's state-run Korean Central News Agency (KCNA) said North Korean leader Kim Jong-il received Putin's envoy Konstantin Pulikovsky, who delivered a personal letter from the Russian president.

KCNA gave no details on the letter, which reached Kim days before a slated visit to South Korea by U.S. President George W. Bush.

The brief KCNA report on Pulikovsky's visit focused on economic issues .

During meetings in Pyongyang, Pulikovsky told Kim Russia was eager to follow up on pledges made at the Kim-Putin summit in Moscow in August to shore up energy, transport and industrial cooperation, Reuters quoted KCNA as saying.

With its ties with the United States and South Korea strained last year, North Korea moved to strengthen its relationship with Moscow. Russia helped establish the communist government of Kim's father Kim Il-sung in the northern half of the Korean peninsula in 1948.

North Korea has also sought support for its other cold war communist patron, China, which Kim Jong-il visited on secretive tours in mid-2000 and early 2001.

The North Korean News Agency said the North's Committee for the Promotion of International Trade signed a cooperation agreement on Tuesday with Russia's Far East Investment Company.

North Korea and Russia agreed last year to cooperate on opening railway links between Europe and South Korea through Russia and North Korea. Under the project, Russia would help upgrade North Korea's dilapidated rail system.