Speaking at a US congressional hearing, Gates said the new anti-missile system would integrate sea-and land-based missile defence systems, according to a Reuters report.
Gates explained the need for the system:
"One of the elements of the intelligence that contributed to the decision on the phased adaptive array (approach) was the realization that if Iran were actually to launch a missile attack on Europe, it wouldn't be just one or two missiles, or a handful. It would more likely be a salvo kind of attack, where you would be dealing potentially with scores or even hundreds of missiles."
Once the new system was in place, Gates said it:
Would give us the ability to protect our troops, our bases, our facilities and our allies in Europe."
He added that not only Iran and North Korea might have missiles in 10 years’ time:
"I think by 2020 we may well see it from other states, especially if we're unsuccessful in stopping Iran from building nuclear weapons."
American intelligence has warned of Iran’s missile threat for a long time, Pentagon press secretary Geoff Morrell told a news conference
"We are clearly dealing with a country that has made no secret of its desire to develop a robust, plentiful, increasingly capable missile arsenal."
He did point out; however, the intelligence was "an imperfect science."
"We have been proven wrong before. We have had to make adjustments."
Morrell explained the Obama government’s approach:
“Will allow us the flexibility so that as intelligence changes, as the situation changes in these rogue states developing long-range and medium-range missile capabilities, we will have the wherewithal to adjust our defences."
The multibillion-dollar program is designed to defend Europe itself and US military targets against a potential Iranian missile attack with chemical, biological or even nuclear-tipped missiles.
Update -- According to Missilethreat.com
Iran has directly threatened Israel and is seen to pose a threat to the US via third-party users of its technology. The potential threat against Europe is apparently based on the projected range of the new missiles.