Aides to President Trump are digging through a menu of options including taxes and fees that would back up his campaign pledge to force Mexico to pay for a border wall.

The array of options include slapping a tax on payments immigrants send to family members back in Mexico, tweaking trade deals, and requiring skilled workers from other countries to pay.

All are 'indirect' forms of payment – and come as Trump is demanding Congress provide $25 billion for a 'trust fund' to pay for the wall as part of a broader immigration deal.

A former advisor in close contact with the White House told McClatchy Trump 'will find a way,” adding: 'The wall will be funded partially or all by an additional revenue stream.'

President Trump is weighing 'indirect' ways to try to force Mexico to pay for a border wall

One idea already being floated is to tax 'remittances' that immigrants from Mexico send home. Remittances to Mexico totaled $29 billion in 2016 according to the report. But getting the revenue into the U.S. treasury could be a problem if people turn to ways to get around the tax.

A $2,500 fee on high-tech workers also being proposed. The high-tech workers who come here on H1-B visas would pay the fee in order to get expedited green cards. It could raise an estimated $4 billion, according to sponsor Rep. Kevin Yoder of Kansas.

But most of these workers hail from China and India, not Mexico.

Trump repeatedly said during the campaign he would force Mexico to pay, even as its leaders refused. 'Who's going to pay for the wall?' Trump would ask, as audience members would shout out: 'Mexico!'

Backing away from that pledge could be politically problematic. Trump has showed more flexibility in recent tweets.

A border patrol agent drives along the US- Mexico border crossing on January 26, 2017 in San Ysidro, California

Residents wait in line at the Banco Azteca banking outlet in Zamora, Michoacan, that handles Western Union wire transfers from the U.S. A large majority of the residents throughout Michoacan have relatives working in the U.S. and they rely on the money sent by relatives working in the U.S.

Homeland Security secretary Kirstzen Nielsen listens as President Donald Trump speaks during a meeting with law enforcement officials on the MS-13 street gang and border security, in the Cabinet Room of the White House, Tuesday, Feb. 6, 2018

'The Wall will be paid for, directly or indirectly, or through longer term reimbursement, by Mexico, which has a ridiculous $71 billion dollar trade surplus with the U.S.,' Trump tweeted last month. 'The $20 billion dollar Wall is “peanuts” compared to what Mexico makes from the U.S. NAFTA is a bad joke!'

He also wrote: 'The Wall is the Wall, it has never changed or evolved from the first day I conceived of it. Parts will be, of necessity, see through and it was never intended to be built in areas where there is natural protection such as mountains, wastelands or tough rivers or water.....'

House Homeland Security chair Rep. Michael McCaul of Texas spoke about border security at a White House meeting that included Trump Tuesday – but using technical language beyond simply calling it a 'border wall.'

McCaul called it 'border security authorizing a wall-barrier system and technology and personnel and boots on the ground.'

Trump has also floated funding the wall through tariffs, but such a move could provoke counter-measures and force consumers to pay higher prices. The administration is in the process of renegotiating NAFTA and could try to steer funds from there to wall construction.

'The wall offer’s off the table,' said Minority Leader Charles Schumer of New York last month, withdrawing an offer he presented to Trump to fully fund the wall in a deal to provide status for DREAMers and avoid a government shutdown that ended up happening anyway.