Iranian President Hassan Rouhani told North Korea's foreign minister that the United States cannot be trusted, Tehran's state media said, as the United States seeks a deal to rein in the North's nuclear and missile programmes.
North Korea for its part denounced the United States for its "outdated acting script" in pressuring the North with continued sanctions, but said it was still prepared to meet its obligations after a historic North Korea-U.S. summit in Singapore in June.
Iran dismissed a last-minute offer from Washington for talks this week, saying it could not negotiate after the Trump administration reneged on a 2015 deal to lift sanctions in return for curbs on Iran's own nuclear programme.
North Korea's top diplomat, Ri Yong Ho, visited Iran as the United States reintroduced sanctions against the Islamic Republic.
"The U.S. administration performance in these years has led the country to be considered untrustworthy and unreliable around the world which does not meet any of its obligations," Rouhani was quoted by the Islamic Republic News Agency (IRNA) as telling Ri on Wednesday.
"In the current situation, friendly countries should develop their relations and cooperation in (the) international community," he said, adding Iran and North Korea have "always had close views" on many issues.
Ri travelled to Tehran after attending a security forum in Singapore, where he and U.S. Secretary of State Mike Pompeo sparred over an agreement made at June's landmark summit between Trump and North Korean leader Kim Jong Un.
The two sides vowed to work towards North Korea's denuclearisation at the summit, but have since struggled to reach a deal to meet that goal, with the United States insisting sanctions pressure must be maintained.
North Korea's foreign ministry said on Thursday it had stopped testing missiles and conducting nuclear tests "followed by dismantling the nuclear test ground", and yet the United States still had insisted on "denuclearisation first".
North Korea nevertheless went ahead with the return of the remains of U.S. soldiers killed in the 1950-53 Korean war, it said.
"We hoped that these goodwill measures would contribute to breaking down the high barrier of mistrust existing between the DPRK (North Korea) and the U.S. and to establishing mutual trust," it said in a statement carried by the North's KCNA news agency.
"However, the U.S. responded to our expectation by inciting international sanctions and pressure against the DPRK."
The United States was "attempting to invent a pretext for increased sanctions against the DPRK by mobilising all their servile mouthpieces and intelligence institutions to fabricate all kinds of falsehoods..."
"As long as the U.S. denies even the basic decorum for its dialogue partner and clings to the outdated acting script which the previous administrations have all tried and failed, one cannot expect any progress in the implementation of the DPRK-U.S. joint statement including the denuclearisation...
"We remain unchanged in our will to uphold the intentions of the top leaders of the DPRK and the U.S. and to build trust and implement in good faith the DPRK-U.S. joint statement step by step. The U.S. should, even at this belated time, respond to our sincere efforts in a corresponding manner."
Ri told Rouhani that Washington's pullout from the 2015 pact and restoration of sanctions was an "action against international rules and regulations", IRNA said.
"North Korea's strategic policy is to deepen relations with the Islamic Republic of Iran and confront unilateralism," he said.
