Dockworkers began picketing at the Port of Philadelphia early Tuesday after the International Longshoremen's Association announced the union would go on strike​.

With a potential strike at ports up and down the East Coast and along the Gulf Coast set to begin after midnight Monday, logistics executives tell CNBC the remaining hours are critical in moving out as much trade as possible before a shutdown that will do serious damage to the functioning of the U.S. economy.

Dockworkers have walked out of every major port on the US East and Gulf coasts, marking the beginning of a strike that could ripple through the world’s largest economy and cause political turmoil just weeks before the presidential election.