As North Korea prepared to show the world its nuclear muscle, US Ambassador to the United Nations Susan Rice said the test would be a blatant violation of its international obligations under Security Council resolutions.
"I anticipate that the council would convene to discuss this and to respond in a credible fashion, to both the missile launch and to any potential additional subsequent actions," Rice told CNN. Echoing this, Pentagon spokesperson George Little said the missile launch would be regarded as a serious provocation.
Little said the US defence secretary Leon Panetta had discussed the latest developments with South Korea's defence minister by phone.
A South Korean government official said the UN may issue a warning to North Korea, the Chos Unilbo newspaper reported.
The Washington Post quoted North Korean space officials as saying that all assembly and preparations for the satellite launch had been completed. Officials denied it was a cover for a missile test.
The officials said in Pyongyang that the launch of the three-stage rocket was on schedule between 12-16 April to coincide with the centennial birthday commemorations for the late president, Kim Il Sung, North Korea's founder.
A South Korean report suggested all activities at the atomic testing site were similar to that of earlier detonations. Another unidentified source also confirmed that the excavation was almost complete at the same site where the country previously carried out two nuclear tests in 2006 and 2009, AP reported.
South Korean intelligence claimed that satellite images had confirmed the north's preparations in Punggye-ri, North Hamgyong province. The South Korean Yonhap news agency quoted an unnamed intelligence source as saying North Korea was "clandestinely preparing a nuclear test".
China and Japan were also reportedly keen to discourage North Korea from launching the missile.
North Korea said it will only be sending a weather satellite into space, whereas both South Korea and the United States view it as a ballistic missile test.
Amidst mounting tension, many flights across the region are being rerouted.