President Donald Trump vetoed a congressional resolution that was blocking his border wall emergency.

A Pentagon decision to spend up to $1 billion to build 57 miles of fencing along the Mexican border drew an angry response Tuesday from Democrats who claimed “political interference” could harm military readiness.

Acting Secretary of Defense Patrick Shanahan on Monday authorized the commander of the Army Corps of Engineers to plan and build the 18-foot-high fencing, construct and upgrade roads and install lighting in Yuma, Arizona, and El Paso, Texas.

Shanahan said the efforts was in support of the national emergency declaration President Donald Trump issued last month for the southern border. Trump issued the declaration after Congress refused to appropriate the $5.7 billion he wanted for construction of the wall.

Trump has repeatedly claimed the wall is needed to keep criminals from entering the U.S. Shanahan cited the need to “block drug-smuggling corridors across international boundaries of the United States in support of counter-narcotic activities of federal law enforcement agencies.”

Democrats immediately expressed outrage, with several senators on the Senate Appropriations Committee signing a letter blasting Shanahan or failing to seek approval of the congressional defense committees.

“We have serious concerns that the department has allowed political interference and pet projects to come ahead of many near-term, critical readiness issues,” the letter said.

Shanahan, in testimony Tuesday before the House Armed Services Committee, reiterated his claim that the transfer of funds to the wall won’t jeopardize national security.

Shanahan announced the plan late Monday, hours before the U.S. House was schedule to vote on Trump’s veto of a congressional resolution that would have voided the emergency declaration. Foes of Trump’s plan, however, did not appear to have the two-thirds majority required to override.

“The President’s veto will be upheld,” Tweeted Minority Leader Kevin McCarthy, R-California. “We will #SecureTheBorder.”

Trump says his declaration of a national emergency to build the wall allows him to tap billions targeted for military construction projects ranging from garages and air traffic control towers. The projects have been approved by Congress but contracts have not yet been signed.

Last week, Shanahan forwarded to Congress the list of construction projects the Pentagon could delay but not cancel to redirect funds to the wall.