The damage bill from Tropical Storm Harvey is likely to be enormous, and that leaves US President Donald Trump with a tough decision to make.

He wants Congress to approve the funds he needs to start building his border wall with Mexico, and he's promised to shut down the Government if it doesn't, but doing so in the wake of such a huge natural disaster is risky.

Here's why.

Texas wants at least $125 billion for Harvey disaster relief

It's not yet known how much aid Texas will need to recover from Harvey, but it's expected to be many billions of dollars.

Texas Governor Greg Abbott has said he'll need at least $125 billion from the US Government to rebuild.

That's how much the Government allocated to the recovery effort in the wake of Hurricane Katrina back in 2005, but Mr Abbott says Harvey is bigger and may need more.

Sorry, this video has expired Drone footage shows devastation caused by Harvey

But there are actually plans in motion to cut disaster funding

Next week, the House is scheduled to consider a massive spending bill that plans to cut $876 million from the Federal Emergency Management Agency's (FEMA) disaster relief account.

The plan was for that money to go towards a $1.6 billion down payment for Mr Trump's wall.

(ICYMI: Mr Trump promised during his election campaign that Mexico would pay for the wall — which experts say will cost $22 billion to build — but Mexico has refused to do that, so the US will now need to foot the initial bill).

Although obviously that would look really bad right now

Those cuts were proposed well before Harvey hit Texas, so its likely Republican leaders will move to scrap them.

But the President has promised to shut down the Government if Congress doesn't include the funding in the next spending deal.

"If we have to close down our Government, we're building that wall," he told supporters at a campaign-style rally in Phoenix last week.

Sorry, this video has expired Trump 'openly called for unity, healing and love'

So here's the dilemma...

Republicans need at least eight Democratic votes in the Senate to pass a spending deal with funding for the wall, but Democrat leaders firmly oppose it and don't appear to want to do Mr Trump any favours.

That means its unlikely Congress will be able to agree to a deal.

Normally that would mean a Government shutdown, but its widely expected that if that happens, the Senate will simply scrap the funding from the deal.

That would leave Mr Trump with three major options

He could:

Veto the deal and cause a government shutdown

Veto the deal and cause a government shutdown Let it through and go back on his promise of a government shutdown; or

Let it through and go back on his promise of a government shutdown; or Sign a short-term extension without wall funding and delay it even further

Vetoing the spending bill would put Mr Trump in a dangerous position, because for one, it would mean rejecting a bill approved by his own party.

"Shutting down the Government would be a self-destructive act, not to mention an act of political malpractice," Republican Representative Charlie Dent said in an interview.

In addition, it would also delay many of his other plans, including a sweeping revamp of the tax code. A shutdown debacle would make that extra difficult.

And finally, according to a Vox report, a shutdown would mean, "federal agencies like FEMA and the flood insurance program would be effectively crippled at the very moment they're most needed".

But letting the legislation through would mean Mr Trump would break his promise to take strong action.

And if he signs a short-term extension without wall funding, it could delay the battle until later this year, possibly December.

So what will Mr Trump do?

At the moment he seems unwilling to back down. ( AP: Alex Brandon )

On Monday he said the hurricane recovery effort had not caused him to reconsider a shutdown.

"I think it has nothing to do with it, really. I think this is separate," he said at a news conference.

He said he hoped it wouldn't happen, but declined to rule it out.

"If it's necessary, we'll have to see," he said.

And meanwhile, Mexico has offered to help Harvey victims

Because, according to its statement, that's what "good neighbours should always do in difficult times".



ABC/wires