Funds made available under subsection (a) of section 104 of this title may be used to pay the entire engineering costs of the surveys, plans, specifications, estimates, and supervision of construction of projects for such urgent improvements of highways strategically important from the standpoint of the national defense as may be undertaken on the order of the Secretary and as the result of request of the Secretary of Defense or such other official as the President may designate. With the consent of a State, funds made available under subsection (b) of section 104 of this title may be used to the extent deemed necessary and advisable by the Secretary to carry out the provisions of this section.