Secretary of Defense Mark T. Esper speaks about defense challenges at the Royal United Services Institute in London on Sept. 6. (Facundo Arrizabalaga/EPA-EFE/Shutterstock)

Defense Secretary Mark T. Esper said he is urging European allies to pick up the tab for military construction projects in their countries defunded by the Pentagon to pay for President Trump’s border wall.

The comments come after the Defense Department announced 127 construction projects that it plans to defund to free up $3.6 billion for 175 miles of fencing and barriers on the southern border with Mexico. Among the defunded initiatives is some $770 million worth of construction projects in Europe that are designed to help U.S. allies better defend themselves in the event of an attack by Russia.

Esper, who made the comments while on a trip to Europe, emphasized that the Trump administration has been seeking greater “burden sharing” with allies across the board. Trump regularly criticizes NATO allies who he says have failed to contribute enough funds to their defense and rely instead on the U.S. military.

“The message that I’ve been carrying, since when I was acting secretary to today, has been about the increase in burden sharing,” Esper told reporters in London late Thursday, according to Reuters. “So part of the message will be, ‘Look, if you’re really concerned, then maybe you should look to cover those projects for us,’ because that’s going to build infrastructure in many cases in their countries.”

“Part of the message is burden sharing, ‘Maybe pick up the tab,’ ” Esper added.

An obscure section of the U.S. code governing the military allows the defense secretary, in the event of a national emergency requiring the use of the armed forces, to undertake military construction projects in support of those forces without sign-off from Congress. The law allows the defense secretary to use money that Congress has appropriated for other military construction projects but which hasn’t yet been contracted.

Earlier this week, the Pentagon announced that Esper would be using that law to take $3.6 billion that Congress appropriated for other military construction projects and divert the funds to the construction of new barriers on the southern border. Esper determined that the barriers in question would support troops Trump has deployed as part of the national emergency he declared in February.

There are about 3,000 active duty troops and 2,000 national guardsmen serving on the border, where they are helping ease the burden on Customs and Border Protection caused by an influx of primarily Central American migrant families.

The Pentagon says it is committed to seeing through the defunded programs and is urging Congress to replenish the funding by “backfilling” the money. To do this, Congress would need to appropriate funds for projects it has already appropriated funds for in the past.

Republican lawmakers largely have agreed to do so, but Democrats have balked, saying Trump’s move to take Pentagon funds without approval from Congress flies in the face of its constitutionally mandated power of the purse. Should Congress ultimately decide to replenish the funding, many of the projects could proceed without delay, because they are scheduled to award their contracts in future years.

More than $770 million worth of defunded projects are for the European Deterrence Initiative and its predecessor program, which President Barack Obama launched in 2014 to shore up the defenses of European allies after Russia annexed Crimea from Ukraine.

The affected initiatives include a plan to build a facility for Special Operations forces and their training in Estonia, projects to construct ammunition and fuel storage facilities and staging areas in Poland, and planned upgrades to surveillance aircraft facilities in Italy, as well as airfield and fuel storage upgrades in Slovakia and Hungary.