Elon Musk said on Friday his rocket company SpaceX cannot indefinitely fund its Starlink internet service in Ukraine, which has helped the country's civilians and military stay online during the war with Russia.

Musk's comment on Twitter came after a media report that SpaceX had asked the Pentagon to pay for the donations of Starlink. The billionaire has been in online fights with Ukrainian officials over a peace plan he put forward which Ukraine says is too generous to Russia.

The billionaire who runs Tesla said Starlink says he spends nearly $20 million a month for maintaining satellite services in Ukraine. He recently said that SpaceX had spent about $80 million to enable and support Starlink there.

"SpaceX is not asking to recoup past expenses, but also cannot fund the existing system indefinitely *and* send several thousand more terminals that have data usage up to 100X greater than typical households. This is unreasonable," Musk wrote on Twitter on Friday.

"We’ve also had to defend against cyberattacks & jamming, which are getting harder," Musk wrote.

CNN reported on Thursday that SpaceX sent a letter to the Pentagon last month saying it could not continue to fund the Starlink service in Ukraine and it may have to stop funding it unless the U.S. military gives the company tens of millions of dollars a month.

A Pentagon spokesperson said the Defense Department "continues to work with industry to explore solutions for Ukraine’s armed forces as they repel Russia’s brutal and unprovoked aggression."

SpaceX did not respond to a request for comment.

Musk activated Starlink, satellite broadband service, in Ukraine in late February after internet services were disrupted because of Russia's invasion. SpaceX has since given it thousands of terminals.

Starlink has been a key communications tool for Ukrainian forces in their fight against Russian forces.

On the official Ukrainian defense ministry twitter feed, a video shows Ukrainian soldiers singing the praises of the technology. "Thank God we have Starlink. It's a lifesaver," one soldier said according to a translation posted with the video.

Ukraine's vice prime minister, Mykhailo Fedorov, said this week Starlink services helped restore energy and communications infrastructure in critical areas after more than 100 Russian cruise missile attacks

Russia calls its intervention in Ukraine a "special military operation" and says it does not target civilians.

Musk drew widespread criticism from Ukrainians over his peace plan in which he proposed that Ukraine permanently cede the Crimea region to Russia, that new referendums be held under U.N. auspices to determine the fate of Russian-controlled territory, and that Ukraine agree to neutrality.

Ukraine says it will never agree to cede land taken by force, and lawful referendums cannot be held in occupied territory where many people have been killed or driven out.

Ukraine's President Volodymyr Zelenskiy was among those who criticized Musk's proposal.

Ukraine's outgoing ambassador to Germany, Andrij Melnyk, also condemned the plan in tweet that told Musk in profane terms to go away.

Musk, responding to a post referring to the fate of the Starlink service and the ambassador's remark, said:

"We’re just following his recommendation."

Republican U.S. Representative Adam Kingzinger cited Musk's comments on Twitter, writing "if there was ever proof that

@elonmusk is playing games this is it. I’m not sure someone like this can be trusted to any longer do business with our government."

While extremely costly to deploy, satellite technology like Starlink can provide internet for people who live in rural or hard-to-serve areas where fiber optic cables and cell towers do not reach. The technology can also be a critical backstop when natural disasters disrupt communication.

SpaceX's president, Gwynne Shotwell, previously told Reuters that France and Poland were helping fund shipments of Starlink terminals to Ukraine. The U.S. Agency for International Development said in April that it had bought some of the terminals from SpaceX, and that the internet service was made possible by a "range of stakeholders" that included SpaceX's donations.

(Reporting by Shubham Kalia in Bengaluru, David Shepardson and Mike Stone in Washington; Editing by Robert Birsel and Alistair Bell)