North Korea has sent a letter to the UN Security Council rejecting claims it sank a South Korean warship and warning the council not to debate the issue.
The letter also urged the council to facilitate Pyongyang's own investigation into the incident.
It comes as Seoul said it had finished installing loud speakers on its borders to broadcast propaganda to the North.
The Cheonan sank on 26 March, killing 46 sailors. International investigators say a North Korean torpedo sank it.
Seoul last week formally referred the issue to the Security Council.
The letter was reportedly sent by North Korea's UN envoy Sin Son-ho to UN Security Council President Claude Heller and was released by North Korean state media.
It said North Korea had "nothing to do with the incident", describing it as a "fabricated scenario" masterminded by the US.
The key to resolving the dispute was allowing Pyongyang's investigators to verify the international panel's findings in a "scientific and objective" manner, it said.
The letter warned of consequences if the issue was put on the council's agenda for debate without North Korea having been allowed to conduct its own investigation.
This would make it "more than clear that the sovereignty and security of the DPRK [North Korea] is infringed upon, and by then no-one would dare imagine how serious its consequences would be with regard to the peace and security on the Korean Peninsula," it said.
South Korea has rejected the North's request to send its own investigators.
It is not yet clear whether South Korea is seeking additional sanctions against its communist neighbour or some form of weaker statement.
UN sanctions are already in place against North Korea in the wake of its two nuclear tests in 2006 and 2009.
The warship row has left inter-Korean relations highly tense. Seoul has suspended inter-Korean trade and Pyongyang responded by cutting all ties.
On Wednesday, South Korea's army said it had finished installing a series of loudspeakers at 11 points along its border, to broadcast propaganda messages into the North, the Yonhap news agency reports.
The speakers were dismantled six years ago as relations improved but Seoul said it would restore them after tensions rose in the wake of the Cheonan report.
Seoul gave no date when the speakers will be turned on - Pyongyang has said it will fire on them when they are.
However, also on Wednesday Seoul approved two shipments of baby food to be sent to the North.
North Korea suffers from severe food shortages and relies on foreign help to feed its people.
Unification Ministry spokeswoman Lee Jong-joo said the aid, with a total value of $320,000 (£221,000), would be sent to day-care centres in the North East and near Pyongyang.
"While South Korea will, in principle, hold off on inter-Korean business projects, we will continue providing purely humanitarian aid for the weak like infants and children," she said.