Foreign ministry spokesman Bahram Ghasemi was responding to a tweet by Trump over the weekend in which the US president wrote: "Iran just test-fired a Ballistic Missile capable of reaching Israel. They are also working with North Korea."
Ghasemi said there were "no similarities nor resemblance" with the actions of North Korea, and that claims they were working together on ballistic missile development amounted to a "clear lie".
"It is very clear that this is a nonsense and baseless claim," he told reporters.
The indigenously-built Khorramshahr was first announced by the defence ministry in September 2016, and US officials said it was this ballistic missile was tested in January, sparking international condemnation.
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However, Iran never confirmed that the January test was the Khorramshahr missile.
There has been speculation, particularly from hawks in Washington, that the Khorramshahr was based on North Korea's intermediate-range Musudan missile.
In 2010, a diplomatic cable released by Wikileaks showed that US intelligence officers believed North Korea had shipped Musudan missiles to Iran.
A detailed report earlier this year by the US-Korea Institute at John Hopkins University in the United States found: "The available evidence cannot verify speculation that the Iranian missile is similar to North Korea's Musudan".
Iran and North Korea have cooperated on military technology in the past.
During Iran's war with Iraq in the 1980s, it turned to North Korea as one of the only sources of military assistance, importing a stockpile of Nodong missiles.
Iran used the Nodong to develop its own medium-range Shahab-3 missile, first tested in 1998, and it has continued to improve on the design since.
Instead, Iran has emphasised its home-grown missile programme, and denied that this breaches any international laws.
"Since the criticism of American officials, the speed of missile development has increased several times," said General Amir Ali Hadjizadeh, head of aerospace forces for the Iran's elite Revolutionary Guards, according to state television today.
"All the materiel and pieces for our missiles are manufactured locally and do not come from abroad," he said.
He said the Khorramshahr missile was 13 metres (43 feet) long and could carry an 1,800 kilogram (almost 4,000-pound) payload.
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