Texas Governor Greg Abbott has asked US President Donald Trump to issue a "major disaster declaration" for the state, as Hurricane Harvey threatens to inflict some of the worst storm damage in a decade.
With the powerful storm just hours from slamming full-force into Texas's Gulf coast, Mr Abbott warned that Harvey was "turning into a very complex and dangerous hurricane".
"We can obviously tell already at this stage this is going to be a very major disaster," he said.
Mr Abbott told reporters he had requested "moments ago" that Mr Trump make the disaster declaration in order to "trigger additional help and assistance from the federal government".
Meanwhile, White House press secretary Sarah Sanders has said: "The president will make plans to go to Texas early next week," shortly before Trump left for the Camp David presidential retreat in Maryland, where he plans to spend the weekend.
Mr Trump has tweeted: "I encourage everyone in the path of #HurricaneHarvey to heed the advice & orders of their local and state officials."
I encourage everyone in the path of #HurricaneHarvey to heed the advice & orders of their local and state officials. https://t.co/N6uEWCZUrv
— Donald J. Trump (@realDonaldTrump) August 25, 2017
Harvey became a Category 3 hurricane, the third most powerful, according to the National Hurricane Center.
Authorities have warned locals to shelter from what could be life-threatening winds and floods.
Harvey is set to make landfall late today or early tomorrow on the central Texas coast where Corpus Christi and Houston are home to some of the biggest US refineries.
Oil and gas operations have already been disrupted and gasoline prices have spiked.
"Now is the time to urgently hide from the wind. Failure to adequately shelter may result in serious injury, loss of life, or immense human suffering," the National Weather Service said.
Now is the time to complete preparations. Tropical-storm-force wind gust recently reported at the Corpus Christi Naval Air Station. #Harvey pic.twitter.com/jlw3lEPTEj
— NHC Atlantic Ops (@NHC_Atlantic) August 25, 2017
The threat has triggered evacuations and cancelled the first day of school in communities along the south Texas coast, which is home to 5.8 million people from Corpus Christi to Galveston.
Up to 97cm of rain are expected over parts of Texas, with winds up to 201km/h, and sea levels may surge 3.7m.
"Life-threatening and devastating flooding expected near the coast due to heavy rainfall and storm surge," the NHC said.
The storm's approach triggered evacuations and forced classes to be cancelled at dozens of schools along the south Texas coast, home to 5.8 million people from Corpus Christi to Galveston.
Harvey also forced the cancellation or delay of at least 40 flights in and out of major airports in Texas, according to Flightaware.com, which tracks airline traffic.
Harvey has already disrupted US oil supplies in the region.
Three refineries in Corpus Christi and one farther inland at Three Rivers were shutting down ahead of the storm.
Royal Dutch Shell Plc, Anadarko Petroleum Corp and Exxon Mobil Corp have evacuated staff from offshore oil and gas platforms in the storm's path.
The US government said 9.6% of crude output capacity was shut and 14.6% of natural gas production was halted.
The storm could also bring flooding to shale oil fields in southern Texas that produce more than one million barrels of oil a day.
EOG Resources Inc said it has curtailed drilling and shut in some production in the Eagle Ford shale region.
Noble Energy Inc and Statoil ASA also said it was evacuating some staff from production facilities.
Louisiana and Texas declared states of disaster, authorising the use of state resources to prepare.
An American cruise company, Carnival Corp, has said that three of its cruise ships are unable to return to the Port of Galveston, Texas, which is closed ahead of Hurricane Harvey.
Two of the ships, the Carnival Freedom and the Carnival Valor, will head for New Orleans where they will pick up fresh supplies.
Passengers will have the option of disembarking there, but Carnival advised them to not do so and said the ships will return to Galveston as soon as feasible.
A third ship, the Carnival Breeze, will extend its stay in Cozumel, Mexico, and begin sailing back to Galveston this weekend, the company said.
The next scheduled cruises on all three ships will be shortened and customers will receive refunds, the company said.
"We will continue to remain in close contact with port officials regarding their plans to re-open once the storm has passed," a spokeswoman for the company said.
