The White House has said construction could begin quickly on President Trump’s border wall using “existing funds and resources” from the Department of Homeland Security, but a DHS document says the agency so far has identified just $20 million that could be redirected to the project, Reuters reported Wednesday. The document, which was given to congressional budget staff last week, said the available money would only cover a few contracts for wall prototypes, not actual barrier construction on the Mexican border. That suggests that Congress will have to dedicate money to start construction. An internal DHS document estimated that lining the entire Mexico border with walls and fencing could cost $21.6 billion, although Republicans put the cost at $12 billion to $15 billion. House Speaker Paul Ryan says he will include funding for the project in the next federal budget.