Washington (CNN) Secretary of Defense Mark Esper has authorized the diverting of $3.6 billion in military construction funds for 11 wall projects on the southern border with Mexico, according to defense officials and a letter from Esper to the Senate Armed Services Committee, which has been obtained by CNN.

In his letter, Esper told Congress he has "determined that 11 military construction projects along the international border with Mexico, with an estimated total cost of $3.6 billion, are necessary to support the use of the armed forces in connection with the national emergency."

The letter does not include the word "wall," as is typical in Defense Department announcements of this kind, but details how the funds will be used for new fencing projects at various border locations.

The announcement fulfills a promise made by President Donald Trump in February to tap military construction funds to build his border wall. The move was slammed by Congress when it was first announced and only recently completed a Pentagon legal review.

On Tuesday, Senate Minority Leader Chuck Schumer called the decision "a slap in the face" to service members.

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