More than one-third of the money President Donald Trump wants to redirect from other federal programs to build a border barrier is likely to be unavailable from the sources he has identified.

As a result, it may be difficult for the president to circumvent Congress, even if a resolution disapproving of his “emergency” moves is never enacted.

Trump announced Feb. 15 that, using emergency powers, he wants to divert as much as $6.7 billion from other programs to finance the construction of barriers along the U.S.-Mexico border. That includes $3.6 billion from unspent military construction money, $2.5 billion in unspent Pentagon counterdrug funds and $600 million from a Treasury Department asset forfeiture account.

But the Defense Department has told lawmakers that only $85 million remains unspent in the counterdrug account, a House Appropriations spokesman said Thursday.

The Pentagon is planning to ask Congress for authority to reprogram more than $2.4 billion from other military programs into the counterdrug account in order to then take it right back out and move it to the wall project.