Speaking en route to London just ahead of US President George W. Bush, who was arriving later Tuesday for a state visit, Powell said Washington wants to see "trigger mechanisms" to bring more pressure to bear on Tehran.
"The resolution draft we saw earlier in the day (during talks in Brussels between Powell and EU foreign ministers) was just deficient," the secretary of state said.
"I know that even doctor ElBaradei thought it was inadequate to the report he had prepared," he said, referring to International Atomic Energy Agency chief Mohammed ElBaradei and his assessment of Iran's nuclear program.
Powell said the resolution "being presented by the EU three (Britain, France and Germany) was not adequate".
"It did not have (diplomatic) trigger mechanisms in case of further Iranian intransigence or difficulties," he said.