A secret report from the United Nations' nuclear watchdog warns that Iran has the ability to make a nuclear bomb and is developing a missile system to carry it -- an assessment that could call into question the Obama administration's claim on Thursday that the biggest threat from Iran comes from its short- and medium-range missiles. 

Just hours after President Obama and Defense Secretary Robert Gates announced that they were shelving plans for a missile defense shield in Eastern Europe because of Iran's shift in strategy, the Associated Press revealed details of the secret report by the International Atomic Energy Agency. It says Iran has "sufficient information" to build a bomb. 

The report, which says Iran is likely to "overcome problems" on developing a delivery system, appears to be the so-called "secret annex" on Iran's nuclear program that Washington has said is being withheld by the IAEA's chief. 

But the IAEA pushed back hard against that allegation, saying the charge is baseless. 

"With respect to a recent media report, the IAEA reiterates that it has no concrete proof that there is or has been a nuclear weapon program in Iran," the IAEA said in a written statement.

An IAEA spokesman told FOX News that the next formal report on Iran's nuclear capabilities is expected in November. He said the evidence suggesting Iran has a nuclear weapons program has not been verified. 

But officials in the U.S. and other countries have been warning that Iran is making headway in developing long-range missiles and a nuclear weapon. 

Washington's envoy to the IAEA warned just last week that Iran "is now either very near or in possession" of enough material to make a nuclear weapon. 

Iran also launched a satellite into space in February, a move that suggests the nation is making progress on long-range technology. 

A U.S. State Department official at the time called the satellite launch a development that "establishes the technical basis from which Iran could develop long-range ballistic missile systems." 

Lawmakers suggested Thursday that Obama was ignoring these threats when he shelved the Eastern European-based missile defense shield proposed by former President George W. Bush, which was strongly opposed by Russia. 

"Scrapping the U.S. missile defense system in Poland and the Czech Republic does little more than empower Russia and Iran at the expense of our allies in Europe," House Minority Leader John Boehner, R-Ohio, said Thursday. 

White House Press Secretary Robert Gibbs called the accusations that the U.S. was sacrificing security "unfounded criticism." 

Obama said a redesigned defensive system would be cheaper and more effective against any threat from Iranian missiles. 

The Associated Press contributed to this report.