Iran remains the most active supporter of international terrorism, the US State Department said today in its annual report.
US Defence Secretary Mr Donald Rumsfeld warned that terrorists determined to destroy the US would "inevitably" obtain weapons of mass destruction.
Iraq, Iran, Syria, Libya and North Korea are developing nuclear, chemical and biological weapons and will supply them to terror groups, he said.
"They inevitably will get their hands on them and they will not hesitate to use them," Mr Rumsfeld told a Senate subcommittee in Congress.
Sudan, Libya, Iraq, North Korea, Cuba and Syria were also listed for the eighth year running as state sponsors of terrorism.
Secretary of State Mr Colin Powell warned that terrorists are trying every way they can to get their hands on weapons of mass destruction "whether radiological, chemical, biological or nuclear."
Mr Francis Taylor, the department's counter-terrorism co-ordinator, warned that "additional terrorist attacks are very, very likely."
Iran has intensified its backing for violent Palestinian groups that attack Israel, although it has also reduced its other terror activity, the report said.
Iran continued to supply training, weapons and money to radical Palestinian groups and Hezbollah in Lebanon, while Iraq and Syria also supported terrorist groups fighting Israel.
It said that while some of the seven blacklisted countries had taken steps to "get out of the terrorism business" none had fully removed themselves from involvement in terror activities.
Mr Rumsfeld refused to discuss specific terrorist threats, saying the government sees hundreds a day.