This involves NATO-member Romania, and presents the increasingly dangerous prospect of Russia and a NATO country entering potential clashes.

The Wall Street Journal reported Tuesday that the US has been holding talks with Turkey, Ukraine, and its neighbors about exporting up to four million tons of grain a month by October, using the Danube River route.

"Much of the grain would be sent down the river and via the Black Sea to nearby ports in Romania and shipped onward to other destinations," wrote the WSJ. "Though slower and more expensive, the route would work as an alternative to a Black Sea shipping corridor established last year under an agreement with Russia, Turkey and the United Nations."

Ukraine has also been having to rely on slower and much more expensive, logistically challenging overland routes for more and more of its foodstuff exports, while some 50% of its exports must still flow through Black Sea routes.