Houthi militants based in Yemen have been targeting freighters in the area since November.

They say it's a show of support for Palestinian Islamist group Hamas in its conflict with Israel.

Recent days saw a fresh missile attack, and the attempted hijacking of a ship operated by cargo giant Maersk.

That has forced firms to suspend plans to restart routing vessels through the area.

Instead, many ships are sailing around the southern tip of Africa - a much longer voyage that dramatically increases costs.

Asia-to-North Europe freight rates more than doubled this week as a result.

Washington has been trying to assemble a multinational naval task force to combat the problem, but with limited results.

On Wednesday, U.S. ambassador to the United Nations Chris Lu renewed calls for joint action.

And he singled out one country for much of the blame:

"Iran has long enabled these attacks by the Houthis. Beyond Iran's long-standing provision of financing to aid such Houthi operations, since 2015, it has transferred advanced weapons systems to the Houthis, including unmanned aerial systems, land attack cruise missiles and ballistic missiles used in attacks against maritime vessels."

As much as one third of all global container traffic flows through the Red Sea to or from the Suez Canal.

The attacks threaten to delay deliveries for major retailers like IKEA and Walmart.

And the soaring costs could soon mean higher prices for consumers too.

Freight rates from Asia to the U.S. have been less affected, however.

That's because some cargo destined for the U.S. East Coast can be sent straight across the Pacific to the West Coast instead.