With federal aid for green-tech startups under assault in Washington, Tesla Motors took to the webs last week touting how its $465 million federal loan had helped create hundreds of jobs — but it didn't reveal that it's now asking for more government money. They also won't reveal why they want it or how much they're asking for.

No electric vehicle start-up has been as successful at mining cash so far as Tesla, which founder Elon Musk has raised $620 million for from private investors on top of its U.S. Department of Energy loan to build the Model S sedan and Model X crossover. Musk secured a $100 million deal with Toyota for an electric version of the RAV4, and the company had more than $661 million in cash as of June 30, including $330 million of untapped Energy loans.

All after building about 1,900 cars so far.

Which explains why Tesla felt the need to defend the loan program after Republicans attempted to cut it as part of the ongoing budget battles on Capitol Hill. In a company blog, Tesla contended that the loan had allowed it to add 1,000 jobs, and make plans for an additional 1,000 jobs next year as it ramps output of the Model S.

Yet it took a call from the San Francisco Chronicle for Tesla to disclose that it had asked for another federal loan, in an amount it has declined to disclose. Tesla has previously said it had enough cash to cover the costs of launching the Model S and Model X — but the ramp-up of those vehicles may take years.

Tesla acolytes suspect the loan might pay for a long-rumored "Bluestar" model meant to be an affordable family car. Given the heat on the government's loan program, Musk may have to prove he can launch the Model S without issues before getting another boost from Washington.