Elon Musk has said that SpaceX cannot continue to pay for Starlink internet service in Ukraine indefinitely.
In February, the world's richest man activated his company's satellite Internet system in Ukraine, providing connectivity to the country's military and citizens.
But last month the Tesla owner asked the Pentagon to fund the program instead of him, according to US media.
"SpaceX isn't asking for upfront costs, but it can't fund the existing system indefinitely" He wrote Musk tweeted on Friday, referring to his space company that builds the Starlink system.
Starlink works by providing broadband internet via a network of satellites and has proven vital to Ukraine's military as it struggles to retake the country from Russia.
But the program costs $20m (£18m) a month, according to Musk. He recently reported that SpaceX has spent $80 million so far to keep Ukraine online.
"In addition to terminals, we need to build, launch, maintain and replenish satellites and ground stations," he tweeted.
"We also need to defend against cyber-attacks and interference, which are becoming more frequent."
Ukraine's Deputy Prime Minister Mykhailo Fedorov played down tensions with Musk, tweeting that the billionaire "is among the world's leading private donors supporting Ukraine."
"Starlink is an essential element of our critical infrastructure," he wrote.
A presidential advisor of Ukraine however, he said that Ukraine will find a solution to keep Starlink running.
