A new crisis is threatening to disrupt the transport of a wide range of goods, from agricultural crops to lumber to coal.

If tens of thousands of rail workers strike as soon as Friday in pursuit of better working conditions, that would wreak havoc on the system used to move products from place to place.

The International Association of Machinists and Aeronautical Workers District 19 said Wednesday that 4,900 of its members had rejected a tentative contract that the union had negotiated with the railroads. The union said it wouldn't stop working before Sept. 29 to give negotiations time to reach a better deal.

The congestion at American ports has been caused by a strike. Fresh pressure would be brought to bear on trucking companies, as they complain that they can't find enough drivers. As politicians and the markets wrestle with soaring prices for consumer products, it would stymies the movement of goods.

The rail is a big deal. Flexport is a San Francisco company that manages transportation logistics for multinational companies. There isn't much slack in the trucking system.

The stakes are enormous since rail moves two-fifths of long-distance American freight and one-third of exports. A complex global supply chain relies on the coordinated movements of cargo ships, trains and trucks.

The rest feel the effects if any of those elements suffer trouble.

One of the most consequential innovations in modern history is the shipping container. It has made a boom in international trade.

Before the shipping container, freight of every variety had to be loaded by hand onto ships and rail cars and trucks, which was a messy process that cost a lot. The process was changed when cargo began moving in boxes. For the next stage of the journey, cranes and other machinery were used to move containers from huge ships onto the backs of trucks and rail cars.

Intermodal is a mode of cargo transportation that shortens geography, narrows the seas, and eases the passage of freight across land. The supply chain became more global over the last half century, connecting American consumers to factories in Asia and farmers in the Midwest to hungry markets all over the world.

Shipping containers at the Union Pacific Railroad intermodal facility in Joliet, Ill. Since it emerged in 1956, the container has magnified a boom in international trade.Credit...Tannen Maury/EPA, via Shutterstock

From the water's edge to points across the land, the rail network has been a crucial bridge.

In the US, ships bring containers full of factory goods to American ports, while trains carry them to Chicago and Kansas City, where they are loaded with corn, wheat and other grains. The contents of the boxes are sent back to the coastal ports where they can be processed into cereals, bread and animal feed.

Chemicals from China are brought in containers. They are used as ingredients for paint, cleaning products, and other industrial concoctions in many US factories.

The rail system brings crude oil from Canada into the US and then exports it to Mexico.

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How much is inflation? Your dollar won't go as far tomorrow as it did today due to inflation. The change in prices for everyday goods and services is known as the annual change in prices.

Is there a cause for inflation? It could be due to increased consumer demand. There are developments that have little to do with economic conditions and can cause inflation to rise and fall.

I wonder if inflation is bad. It is dependent on the situation. Moderate price gains can lead to higher wages.

Inflation can affect the stock market. It's difficult for stocks to be affected by rapid inflation. Houses have held their value better than financial assets during inflation booms.

The head of energy analysis at the Oil Price Information Service warned that a strike could cause gasoline prices to go up.

The entire system has been under a lot of stress.

Americans confined to their homes stopped going to restaurants, gyms and entertainment venues and replaced them with kitchen appliances, exercise equipment and electronic gadgets. An astonishing surge of imports overwhelmed the delivery system, overwhelmed ports, and overwhelmed rail networks.

The country is trying to eradicate Covid-19 and has shut down major ports this year. Russia is sowing hunger in poor countries by cutting the availability of grains in both countries.

The Pacific Northwest used to import large quantities of Russian oil, but now relies more on rail to get it.

The Association of American Railroads warned that a strike would cost the economy $2 billion a day.

The U.S. rail system has been described as a weak link. The ports of Southern California are the gateway for 40 percent of American imports and they have struggled to respond to the surge in demand.

The decision by major railroads to reward their shareholders at the expense of their customers has been portrayed by regulators and unions as the cause of the rail network's vulnerability. Almost one-fourth of rail workers lost their jobs in the five years before the swine flu hit.

Precision Scheduled Railroading is when the carriers limit service to reduce their costs.

The chairman of the Surface Transportation Board said during a speech last fall that railroads are carrying less freight today than they were in the past. The emphasis of the railroads has not been on growth. The main focus has been on cutting.

A disruption to the rail system would be the equivalent of “a half a million trucks going off line,” said Oren Zaslansky, chief executive officer of Flock Freight.Credit...Brandon Bell/Getty Images

Mr. Oberman said that the five largest railroads spent $114 billion to buy back their shares in order to boost stock prices.

The railroads are exploiting the crisis they created, a crucial lack of capacity, to fan fears of disruption in seeking leverage to deny their workers fair compensation.

The International Association of Sheet Metal, Air, Rail and Transportation Workers and the Brotherhood of Locomotive Engineers and Train said that the railroads were trying to get the unions to cave into their demands. Corporate terrorism can only be described as Congress caving in to it.

The rail companies argue that a strike would hurt a number of industries, from retail to chemicals to construction.

The rail association said that tens of thousands of rail customer locations depend on railroads to deliver raw materials and finished products.

The White House is under grave pressure from inflation and the prospect of a potent new barrier to cargo distribution has scared them.

The union and company leaders were contacted by Mr. Biden while he was in Boston. Labor Secretary Martin Walsh, Transportation Secretary Pete Buttigieg and Agriculture Secretary Tom Vilsack were trying to broker a deal, according to reports.

The president has been involved, according to the White House press secretary. The harm that American families, businesses and farmers would experience if they were not to reach a resolution has been made clear.

She said that the administration was exploring transportation alternatives in case of a strike.

All of the other industries have been dealing with their own issues. Though shipping and trucking rates have fallen this year, a rail strike would reverse that trend.

A disruption to the rail system would be the equivalent of half a million trucks going off line, according to Oren Zaslansky, chief executive officer of Flock Freight. It would be very painful, and we finally got this thing calmed down.

It would be particularly vulnerable to be an agricultural exporter. Farming operations have struggled to gain access to shipping containers as ocean carriers have concentrated available boxes on their most lucrative routes.

The situation has improved after the passage of a new law. Farmers in the center of the country will find it hard to secure containers if the rail links are not as strong.

The effects of another labor negotiation between dockworkers at West Coast ports and the operators of shipping terminals could make it harder for American imports.

Retailers bringing in goods from Asia have diverted shipments from West Coast ports to East Coast landing points in order to be prepared for possible trouble. They thought they could rely on rail and trucking.

It's possible that maybe not anymore.

According to Spencer Shute, a senior consultant at Proxima, trucking rates are likely to increase. The US economy could be in trouble.

Unloading at a supermarket in Brooklyn. A rail strike could drive up gas prices and trucking rates.Credit...Gabby Jones for The New York Times

Peter Baker and Clifford Krauss both contributed to the report.