Suez Canal

Canal officials said some progress had been made, however, and more tugboats were joining the effort on Sunday.

Alternative arrangements are being put in place in case the operation fails.

Egypt's President Abdul Fattah al-Sisi has ordered preparations to lighten the load of the stranded ship.

Dozens of vessels are stuck, waiting for rescue boats to free the 400m-long (1,312ft) ship, which was knocked off course by strong winds.

Egypt has reopened the canal's older channel to divert some traffic until the grounded ship can move again.

The blockage sent oil prices climbing on international markets.

About 12% of global trade passes through the Suez Canal, which connects the Mediterranean to the Red Sea and provides the shortest sea link between Asia and Europe.

The fighting is taking place near the Bab al-Mandab straight, the strategic southern entrance to the Red Sea and the gateway to the Suez Canal.

The development comes amid land clashes Thursday near the straight between units loyal to President Abed Rabbo Mansour Hadi and rebel forces.