SpaceX is calling for the Pentagon to increase the amount it pays for critical internet service in Ukraine provided by the company’s Starlink service or risk losing it, CNN reported on Friday, with CEO Elon Musk suggesting the move is related to the rejection of his proposed peace plan.

In a letter to the Pentagon last month, Starlink said it can no longer continue to fund the Starlink service in Ukraine as it has, citing costs at $120 million for the rest of the year and close to $400 million for the next 12 months, according to documents CNN said it obtained

“We are not in a position to further donate terminals to Ukraine, or fund the existing terminals for an indefinite period of time,” SpaceX’s director of government sales wrote to the Pentagon in the September letter, according to the report. 

The potential loss of Starlink services in Ukraine is likely to have a detrimental effect on Ukrainian armed forces’ counteroffensive against Russia’s occupation and war in the country, with the Ukrainian military crediting the reliable, lightweight and mobile internet terminals as critical to military and civilian communication. 

Among the documents obtained by CNN are said to include a direct request made to Musk in July by the Ukrainian military’s commanding general, Valerii Zaluzhniy, asking for almost 8,000 more Starlink terminals. 

“SpaceX faces terribly difficult decisions here. I do not think they have the financial ability to provide any additional terminals or service as requested by General Zaluzhniy,” an outside consultant working for SpaceX wrote in a separate letter to the Pentagon, CNN reported.

Mikhail Podolyak, a senior adviser to the office of the Ukrainian president, tweeted Friday that Ukraine expects Starlink to provide connection “till the end of negotiations,” though it was unclear specifically which negotiations he meant.

“Let’s be honest. Like it or not, [Elon Musk] helped us survive the most critical moments of war. Business has the right to its own strategies. [Ukraine] will find a solution to keep [Starlink] working. We expect that the company will provide stable connection till the end of negotiations,” Podolyak said.

The reported Starlink letter to the Pentagon comes as Musk has faced intense scrutiny over his personal opinions and involvement related to Russia’s invasion of Ukraine, including whether he has spoken directly with Russian President Vladimir Putin related to a so-called peace plan the billionaire mogul proposed on Twitter earlier this month, with an accompanying poll.

Musk has denied claims that he spoke with Putin before tweeting about his peace plan, which included recognizing Crimea as part of Russia, codifying Ukraine as neutral and redoing elections in Ukrainian territory claimed by Russia — claims rejected by the majority of the international community.

“I have spoken to Putin only once and that was about 18 months ago. The subject matter was space,” Musk tweeted. 

But Musk has come under withering criticism from Ukrainian officials over the proposal, including from Ukrainian President Volodymyr Zelensky, who posted his own poll asking, “Which [Musk] do you support more?” with options for “one who supports Ukraine” or “one who supports Russia.”

Ukraine’s ambassador to Germany, Andrij Melnyk, responded to Musk’s peace plan in a tweet, saying, “F— off is my very diplomatic reply to you @elonmusk.”

Musk on Friday tweeted, “We’re just following his recommendation,” responding to a tweet citing Melnyk’s response and the potential for Starlink to withdraw its support for the satellites.

Ukrainian officials have said they view diplomacy as the likely end of Russia’s war in their country but warned against negotiating prematurely, saying they believe Russia would use any pause in the fighting to regroup its embattled troops to launch even more devastating attacks on Ukraine.

Ukraine’s armed forces have celebrated a series of victories in recent weeks, including retaking territory once claimed by Russia and an explosion on a critical bridge connecting Russia to the occupied Crimean Peninsula, a move that is said to have caused damage and disruption to Russian military supply lines and has reinforced calls among Ukrainians to retake Crimea from control by Moscow.

But Putin is viewed as growing more unpredictable in the face of the setbacks, launching missile attacks on Kyiv and dozens of other cities across the country earlier this month in retaliation for the bridge explosion and raising concerns that the Russian leader may resort to a nuclear weapon strike in response to increasing pressure criticizing his military campaign in the country.

—Updated at 12:10 p.m.