The State Department, speaking after Iran declared it had ballistic missiles with a range of 2,000 kilometres (1,240 miles) and could produce ones with a greater range, said Washington would continue to work with other nations to address the concerns.

"The United States has had and continues to have serious concerns about Iran's missile programs," deputy spokesman Adam Ereli told reporters.

"We view Iran's efforts to further develop its missile capabilities as a threat to the region and to the United States' interests and all the more so in light of its ongoing nuclear program," he said, repeating US allegations that Iran is actively seeking atomic weaponry.

Tehran has denied the US charges on nuclear weapons but earlier Tuesday, former Iranian president Akbar Hashemi Rafsanjani told a conference on "Space and National Security" that Iran now had "the power to send our missiles up to 2,000 kilometers."

As quoted by Iran's official news agency IRNA, Rafsanjani confined his remarks to the possibilities such missiles would bring to launching a satellite but the United States and its main Middle East ally Israel are deeply concerned by their military implications.

The former president now heads the Expediency Council, Iran's top political arbitration body, and his comments were expected to add to increasing international concerns over the country's weapons capabilities.

Ereli declined to comment specifically on the announcement and whether the United States placed credence in it, but said it was well known that Iran has been in the late stages of developing a medium-range ballistic missile and was working on a longer range system.

"These kinds of long-range missiles ... have been an active area of Iranian weapons development for some time," he said.

"It has been a concern of ours for some time and international cooperation with like-minded countries is important to take steps to address these efforts and that's where we're focusing our efforts," Ereli said.

On August 11, Iran tested an upgraded version of its Shahab-3 missile. Previous figures had put the missile's range at between 1,300 and 1,700 kilometres, already bringing arch enemy Israel and US bases in the region well within range.

After the latest test, Israeli news reports put the range of the new Shahab-3 -- believed to be based on a North Korean design -- at 2,000 kilometres.

During a military parade last month, Iran showed off its array of ballistic missiles draped in banners vowing to "crush America" and "wipe Israel off the map."

Iran insists the Shahab-3 is simply a deterrent, while Israel charges that the Islamic state could have a nuclear warhead by 2007.

Israeli alarm has led to speculation that Israel -- currently believed to be the only nuclear-armed nation in the Middle East -- may launch a pre-emptive strike against Iran's nuclear facilities.

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