ELEFSINA, Greece—An aging shipyard here has a new suitor sizing it up for investment: the U.S. government.

To counter China’s rising global economic influence, Washington has taken a new direction with foreign assistance. Rather than just lend money or promote trade, as in recent decades, the U.S. is now investing dollars overseas to advance American national-security interests. It wants ports, cellular networks and other strategic assets to stay in friendly hands.

At the forefront of this effort is an agency Congress overhauled in 2019, the International Development Finance Corp., or DFC.

“It’s a very significant investment tool that we have to compete” against China, said Rep. Michael McCaul, the top Republican on the House Foreign Affairs Committee.