North Korea has started fuelling a long-rang rocket, preparing it for launch, CNN reported Wednesday, quoting a US military official, dpa reported.

The Stalinist state said it was to launch what it says is a communications satellite between April 4 and 8.

Washington and Seoul suspect the launch serves as cover for testing North Korea's long-rang Taepodong-2 missiles, which are theoretically capable of reaching Alaska and say the launch violates a United Nations Security Council resolution that bans Pyongyang from testing ballistic missiles.

Meanwhile, South Korean experts believe the North has overcome previous technical problems by cooperating with Iran on missile technology and the launch was likely to succeed.

"After the successful launch of the Iranian space launch vehicle, it is believed that the causes of the previous failure of (North Korea's) Taepodong-2 have been removed," defence analyst Kim Byung-yong was quoted as saying South Korea's Yonhap news agency.

Iran has denied any involvement in North Korea's missile programme.