Inspectors found that Iran increased its stockpile of nuclear fuel by as much as 20 percent in the last year and a half despite U.S. President Barack Obama’s claim that Tehran’s nuclear program was frozen, World Tribune reported.

The revelations in a new report today come as the West lead by the United States and the Iranians continue to negotiate a final nuclear accord by a June 30 deadline.

In his State of the Union address on Jan. 20, Obama said: “Our diplomacy is at work with respect to Iran, where, for the first time in a decade, we’ve halted the progress of its nuclear program and reduced its stockpile of nuclear material.”

Inspectors from the International Atomic Energy Agency (IAEA) discovered the increase in Tehran’s nuclear fuel stockpile, according to the N. Y. Times.

If the report is found to be accurate, it would be a huge obstacle to Congress approving Obama’s final deal with Iran.

According to the report, Western officials are confounded as to why Iran would increased its stockpiles while negotiations were ongoing.

Some analysts believe Tehran is looking at contingency plans should the negotiations fail. Others say technical problems may have rendered Iran’s enriched uranium unusable for weapons.