- Congress and the White House are looking to finish a budget deal by Sept. 30
- A dispute over assigning of website domain names is among obstacles to passage
In an unusual alliance, Trump is siding with Texas Sen. Ted Cruz, who is leading the push to prevent it from taking effect Oct. 1.
Congressional sources tell CNN that Trump's late effort to engage on this issue could throw the last-minute negotiations into flux.
"The US should not turn control of the Internet over to the United Nations and the international community," Trump's national policy director, Stephen Miller, said in a statement. "President Obama intends to do so on his own authority -- just 10 days from now, on Oct. 1, unless Congress acts quickly to stop him. The Republicans in Congress are admirably leading a fight to save the Internet this week, and need all the help the American people can give them to be successful."
Cruz has not endorsed his former rival for the GOP presidential nomination, but tweeted out his thanks for Trump's backing his efforts.
"Appreciate @realDonaldTrump's support of our efforts to keep the internet free."
Democrats have been skeptical of Cruz's efforts, siding with tech firms like Google and Facebook who believe it will be better for the Internet Corporation for Assigned Names and Numbers, based in Los Angeles, to take over domain names to improve information sharing across the Internet.
The Internet issue is one of several matters that the two sides still are haggling over as part of the talks.
They have until Sept. 30 to reach a government funding deal, which will also include funding for Zika. The Senate GOP had hoped to reach a deal this week in order to wrap up the session and let their vulnerable incumbents campaign. But business is expected to extend into at least next week.