US President Donald Trump's promise to use existing funds to finance the construction of his much-promised wall on the Mexican border is falling apart, according to Reuters.
Mr Trump promised that the border fence would be financed by using "existing funds and resources" from the Department of Homeland Security (DHS).
The US Customs and Border Protection says that companies would have to submit "concept papers" to design and build prototypes by March 10, and it plans to start awarding contracts by mid-April.
DHS has estimated the total cost to be US$21.6 billion.
It searched within its $376 million budget for border security fencing, infrastructure and technology - and found only $20 million that can be repurposed to the project.
The money would only be enough to fund a few prototypes for the wall.
In order to actually start construction, Mr Trump will need congressional approval to repurpose the Department's funding.
Republican House Speaker Paul Ryan says he will provide funding for the wall in next year's fiscal budget - however he estimated the cost to be significantly lower than the DHS estimate, at between US$12 billion and US$15 billion.
Republicans have said they will not approve any plan that doesn't offset the cost of the wall with equivalent cuts to spending.