US Secretary of State Condoleezza Rice has accused North Korea of wanting to escalate international tensions over its nuclear weapons programme.
Ms Rice is on a four-day regional tour for talks on the crisis
She said she doubted claims that North Korean leader Kim Jong-il had agreed not to carry out a second nuclear test, or that he regretted the first.
Her comments follow media reports that Mr Kim made the pledge to Chinese envoy Tang Jiaxuan when he visited Pyongyang.
Ms Rice is in Moscow for talks expected to focus on the North Korea crisis.
Ahead of her meeting with Russian President Vladimir Putin, Ms Rice met the editors and son of the murdered Russian journalist, Anna Politkovskaya.
Ms Politkovskaya, a harsh critic of President Putin and Russian policy in Chechnya, was gunned down in her apartment building two weeks ago.
A senior American official said the meeting was not meant as a slight to Mr Putin, but was in to support what was left of the free media in Russia.
Ms Rice is on the final leg of a regional tour taking in Japan, South Korea, China and Russia.
The secretary of state was in Beijing on Friday, but she said the Chinese made no mention of Mr Kim agreeing to halt nuclear tests, despite giving her a "thorough" briefing on Mr Tang's visit to Pyongyang.
"I don't know whether or not Kim Jong-il said any such thing," Ms Rice told journalists accompanying her on a flight from Beijing to Moscow.
"Tang did not tell me that Kim Jong-il either apologised for the test or said that he would not ever test again," Ms Rice added.
"The North Koreans, I think, would like to see an escalation of the tension."
Mr Tang, a former Chinese foreign minister, was sent to North Korea on Thursday to deliver a personal message from President Hu Jintao.
Mr Tang did not set out what took place during his meeting with Mr Kim, but said afterwards that the visit had "not been in vain".
Ms Rice is seeking to bolster international support for enforcing UN sanctions imposed after the communist state's 9 October nuclear test.
The Russians condemned the test when it happened, and the Kremlin has made it clear that it does not welcome a nuclear-armed North Korea, but the BBC's James Rodgers in Moscow says there is little sense in the Russian capital that the world faces a clear and immediate threat.
The Russian Defence Minister, Sergei Ivanov, has said that the sanctions against Pyongyang should be lifted if it returns to the negotiating table.
Ms Rice may also raise the issue of Iran and seek Russian support for sanctions over its suspected nuclear weapons programme at her meetings with Mr Ivanov, President Vladimir Putin and Foreign Minister Sergei Lavrov, analysts say.
Russia's troubled ties with Georgia could also be on the agenda.
NEW UN SANCTIONS
Bans sale to, or export from, N Korea of military hardware
Bans sale or export of nuclear and missile related items
Bans sale of luxury goods
Freezes finances and bans travel of anyone involved in nuclear, missile programmes
Allows inspection of cargo to and from N Korea
Stresses new resolution needed for further action
Ms Rice arrives from three days of intensive diplomacy in East Asia over enforcing a Security Council resolution agreed last Saturday in response to North Korea's underground nuclear test.
The resolution includes sanctions targeting North Korea's missile and nuclear programmes, and allows the inspection of cargo going in and out of the country - something some countries fear will raise tensions further.
Ms Rice has come to Russia to see how much understanding it has for the US position, says our correspondent in Moscow.
Like China, Moscow is wary of putting too much pressure on Pyongyang, our correspondent says.