Ukraine on Wednesday accused the United States of helping Russia by failing to warn it of incoming missile strikes and hobbling Kyiv's military response through changes to the Starlink system it uses on the battlefield.
Ukrainian President Volodymyr Zelensky called on US tech billionaire Elon Musk to restore Starlink, which Kyiv says has been slowed down.
"I hope that it's a mistake, maybe huge technical problem," Zelensky told UK journalist Piers Morgan. "I don't know, but we are asking to do it, to switch (it) on."
Former Ukrainian defence minister Mykhailo Fedorov later said that "Starlink’s operation at speeds up to 160 km/h is being restored. Strike drones and interceptor drones should be able to fly again".
Musk said any disruption was the responsibility of the US government, not his SpaceX company.
He drew a distinction between the Starshield system, which Ukraine relies on for battlefield communications, and the parallel Starlink civilian satellite system, which Ukraine also deploys but is not allowed to use for offensive operations.
"Starshield systems are owned and controlled by the US government. Any limits on speed or usage are decided by the US military and ultimately POTUS," Musk said, referring to US President Donald Trump.
Zelensky replied in the affirmative when asked if he felt "betrayed" after Trump announced a diesel-supply deal with heavily sanctioned Moscow.
"It's painful when President Trump chooses one side, not our side," he said. "I think his advisors are wrong. I don't know who is pushing him not to the right side. This is not (the) right side of history,"
Zelensky had framed the lack of warnings from allies about a wave of powerful strikes on Tuesday night and early Wednesday as "completely unjust", and accused Russia of wilfully flouting a supposed "energy ceasefire" announced unilaterally by Trump.
A senior official in Kyiv confirmed that the United States had in recent days threatened to stop providing intelligence about Russian missile launches that Ukraine uses to thwart attacks. Trump denied doing so on Tuesday.
Defence officials also suggested Washington was behind slower speeds reported on some internet terminals which help Ukraine's military hit Russian-occupied territory and operate interceptor drones.
"It's obvious they (the United States) are helping Russia for some reason," the senior official told AFP.
Zelensky adviser Sergiy Beskrestnov said the attacks and Starlink restrictions were more than a coincidence.
"Through their actions, our partners are depriving us of one of the few chances we have to defend the country against jet-powered Shahed drones," he wrote on Telegram.
In Moscow, Kremlin spokesman Dmitry Peskov said Russia was watching for any sign that Washington's backing for Ukraine may have shifted.
"We are carefully noting all this. It is too early to draw any systemic conclusions," he told reporters.
President Vladimir Putin's special envoy on economic cooperation, Kirill Dmitriev, meanwhile said the first contracts on providing diesel to the United States would be signed in the coming days.
"We are in close, hourly contact with the American side, and everything is moving very quickly," he added.
Trump, facing crunch mid-term elections next month, has blamed Ukrainian strikes on Russian oil refineries for the squeeze on fuel supplies and increase in prices at the pump.
But most experts say the real reason is the joint US and Israeli attacks on Iran since late February, which have seen Tehran block off the Strait of Hormuz, a vital route for oil and gas shipments.
Ballistic missiles have now struck the Ukrainian capital, Kyiv, for two nights running, before air raid sirens could sound in time to warn people to take cover in basements, bomb shelters or metro stations.
"Russia has never before shown such ostentatious disrespect toward the United States," said Zelensky, accusing Moscow of squandering a chance to ease hostilities.
The lack of warning has been reported only rarely during the conflict and Ukrainian officials have previously suggested the Russian military's use of hard-to-detect missiles or potential technical issues could be to blame.
Fifteen people were killed around the country in the latest round of strikes, while significant damage to energy facilities and equipment knocked out power to swathes of Kyiv.
Power plants came under ballistic-missile attack in the eastern Kharkiv region, while Zhytomyr in the northwest, Sumy in the northeast and Chernigiv in the north were also hit.
Russia has previously targeted Ukraine's power stations and heating infrastructure, crippling supplies before winter, when temperatures can plummet to as low as -20C.