Kurt Campbell, the assistant secretary of state for East Asian and Pacific affairs, delivered the message in person to Australian Foreign Minister Bob Carr, the Sydney Morning Herald reported Saturday.
"If the missile test proceeds as North Korea has indicated, our judgement is that it will impact in an area roughly between Australia, Indonesia and the Philippines," Campbell was quoted as saying.
"We have never seen this trajectory before. We have weighed into each of these countries and asked them to make clear that such a test is provocative and this plan should be discontinued."
The nuclear-armed North has announced it will launch a rocket in mid-April to put a satellite into orbit, a move the United States, Australia and other nations see as a pretext for a long-range missile test banned by the UN.
On Friday, the North said preparations for the launch "have entered a full-fledged stage of action" and promised unspecified "counter-measures" against opponents of the operation.
It insisted the launch would not breach an agreement announced last month with the United States, under which the North agreed to suspend its uranium enrichment programme and missile tests in return for US food aid.
The move by North Korea`s new leadership has set off alarm bells across the region with the Philippines already calling for help from the United States to monitor the rocket, part of which is expected to land off the archipelago.
Japan is readying missile defence systems to shoot down any rocket that threatens the country. North Korea`s main ally China has urged that "all parties should keep calm and exercise restraint".
Carr said after meeting Campbell that the launch would be "in clear violation of UN Security Council resolutions."
A UN Security Council resolution passed after the North`s missile and nuclear tests in 2009 bans a ballistic missile launch for any purpose.
"The North Korean nuclear and long-range missile plans represent a real and credible threat to the security of the region and to Australia," Carr told the Herald.
Carr added that he and Campbell had "shared views on how both the US and Australia could engage our regional partners and allies to encourage North Korea to abandon its plans".
World leaders including US President Barack Obama are meeting in Seoul next week for a summit officially focused on nuclear terrorism.
UN Secretary General Ban Ki-moon plans to raise the rocket launch at the meeting on Monday and Tuesday.