The presence of 'rogue states' reinforces the need for a €2.6bn European missile shield, German Defence Minister Franz Josef Jung said.
While not naming specific countries, Iran and North Korea have been cited in the past as 'rogue states' that could launch nuclear weapons in the future.
Mr Jung also alluded to Iran's announcement that it can develop uranium on an industrial scale.
'Precisely these latest developments also confirm that such protection makes sense,' Mr Jung said this week.
'Timely precautions must be taken against the foreseeable increase of the range of offensive missiles of certain problem states, even if it concerns long-term developments,' he added.
The US government wants to build a radar station in the Czech Republic and a missile battery in Poland to defend against possible nuclear attacks.
Plans for such a shield have angered Russia and centre-left coalition partners of the ruling German government.
Senior members of Germany's Social Democrats fear it could trigger a new arms race between Russia and the West.
Comments by Mr Jung, a member of the conservative Christian Democrats, are among the strongest yet from a senior German official who favours discussion of the US project.
Iran said on Monday it had begun industrial enrichment of uranium, a process the West fears Iran will use to make atomic bombs.
Tehran says its programme is entirely peaceful.
When asked when he thought Iran could possess a nuclear weapon, Mr Jung said Tehran had a long way to go, if getting an atom bomb truly was its goal.
The US shield would provide some protection for most of Europe but would leave gaps, especially over southern Europe.
NATO defence ministers will discuss the missile shield at a meeting in Brussels this June though no decision is expected.
