At the time, the Iranian government insisted that it was not sending missiles to Yemen, where Shiite Houthi rebels aligned with Iran have taken over much of the country.
As far back as August, Israel was being "blamed" for a series of airstrikes on Iraqi territory. Israel has not neither confirmed nor denied its involvement in the attacks, while Prime Minister Benjamin Netanyahu has hinted at the possibility that it has struck in Iraq.
Iran responded defiantly, saying it was determined to proceed with its disputed ballistic missile programme, which it has repeatedly described as defensive in objective and nothing to do with its nuclear activity.
Israeli and U.S. officials have warned Iran may be planning more attacks.
Mr Trump wants to force Iran to negotiate a new agreement that would place indefinite curbs on its nuclear programme and also halt its development of ballistic missiles.
Iran is believed to possess the largest and most diverse ballistic missile arsenal in the Middle East, according to USA intelligence assessments, with a substantial inventory of close, short and medium range missiles that can strike targets throughout the region.
The Pentagon has also sent 14,000 additional troops to the region since May.
"People are not paying enough attention to the fact that ballistic missiles in the a year ago have been placed in Iraq by Iran with the ability to project violence on the region", according to Slotkin, an expert on Shiite militias who recently visited Baghdad to meet with Iraqi and American officials, says the paper.
But the European letter says that video footage of a test posted on social media on 22 April showed the use of a Shahab-3 booster that was "a Missile Technology Control Regime Category-1 system", according to the Associated Press.
They said the small boat was towed to port and the boat's crew was transferred to the Yemeni Coast Guard.
The United States is concerned about potential Iranian aggression in the near future, John C. Rood, an undersecretary of defense, told reporters on Wednesday, according to the Times, but he provided no details about what prompted the concerns.
France said on Thursday that Iran's ballistic missile activities did not conform with a U.N. Security Council resolution enshrining a nuclear deal with world powers in 2015 and called on the country to respect all of its obligations under that resolution.
The intelligence officials said the missiles threaten USA allies such as Israel and Saudi Arabia, as well as American troops stationed in the area.
The deployment was meant to improve Iran's ability to retaliate against any Western or Arab attacks on its territory, as well as to expand its options for attacking opponents in the region, Reuters said at the time.
In June, Iran shot down a U.S. Navy high-altitude drone, firing a surface-to-air missile in the area of the Strait of Hormuz.