By Pavel Polityuk
KYIV - Ukraine urged its allies on Friday to send more weapons as its forces dug in to slow Russia's military advance through the eastern Donbas region, while a belligerent Moscow warned Western nations of consequences for their reprisals over its invasion.
Signalling that the Kremlin was in no mood for compromise, President Vladimir Putin said continued use of sanctions against Russia risked causing "catastrophic" energy price rises.
Putin's top diplomat Sergei Lavrov clashed with his Western counterparts at a G20 meeting, where they urged Russia to allow Kyiv to ship blockaded Ukrainian grain out to an increasingly hungry world.
Meanwhile, Moscow's envoy to London offered little prospect of a pull-back from parts of Ukraine under Russian control.
Ambassador Andrei Kelin told Reuters that Russian troops would capture the rest of Donbas in eastern Ukraine and were unlikely to withdraw from land across the southern coast.
Ukraine would eventually have to strike a peace deal or "continue slipping down this hill" to ruin, he said.
On the Donbas frontlines, Ukrainian officials reported Russian shelling of towns and villages ahead of an anticipated push for more territory.
A Ukrainian infantry unit on the road to the town of Siversk, whose members spoke to Reuters, had set up positions on the edge of a deep earth bunker covered with logs and sandbags and defended by machine guns.
"Right now it's more of our artillery than theirs, so it's good," said the unit deputy commander. "But there might be incoming soon."
'SCORCHED EARTH TACTICS'
On Thursday, Putin had indicated that current prospects of finding a solution to the conflict were dim, saying Russia's campaign in Ukraine had barely started.
Ambassador Kelin's remarks gave an insight into Russia's potential endgame - a forced partition that would leave its former Soviet neighbour shorn of more than a fifth of its post-Soviet territory.
"Of course it is difficult to predict the withdrawal of our forces from the southern part of Ukraine because we have already experience that after withdrawal, provocations start," Kelin said.
An escalation of the war was possible, he added.
Ukrainian officials, echoing comments by the deputy commander of the infantry unit outside Siversk, said they needed more high-grade Western weapons to shore up the their defences.
Oleksiy Danilov, secretary of the National Security and Defence Council, said Ukraine still did not have enough Western weapons and soldiers needed time to adapt to using them.
U.S. President Joe Biden signed a new weapons package worth up to $400 million for Ukraine on Friday, including four additional high mobility artillery rocket systems (HIMARS) and more ammunition.
The United States started providing the key precision rocket weapon system to Ukraine last month after receiving assurances from Kyiv that it would not use them to hit targets inside Russian territory. Kyiv has attributed battlefield successes to the arrival of the HIMARS.
"When they came in, the Russian war machine could instantly feel its effect," Danilov told Reuters. But more Western military aid was vital, he added.
President Volodymyr Zelenskiy's chief of staff also urged the West to send more heavy weapons to counter what he called Russia's "scorched earth tactics".
"With a sufficient number of howitzers, SPG and HIMARS, our soldiers are able to stop and drive the invaders from our land," Andriy Yermak wrote on Twitter.
Ukraine has not used HIMARS to strike Russian targets outside of Ukraine territory, a senior U.S. defense official said on Friday, disputing Russian accusations.
'NOT YOUR COUNTRY'
At the G20 meeting in Bali, Indonesia, some of the staunchest critics of the invasion that began on Feb. 24 confronted Lavrov, who walked out of a meeting and denounced the West for "frenzied criticism."
High on the list of foreign ministers' concerns was getting grain shipments from Ukraine out through ports blocked by Russia's presence in the Black Sea and naval mines. Ukraine is a leading exporter and aid agencies have warned that many developing countries face devastating food shortages if supplies fail to reach them.
U.S. Secretary of State Antony Blinken urged Moscow to let Ukrainian grain out, a Western official said.
"He addressed Russia directly, saying: 'To our Russian colleagues: Ukraine is not your country. Its grain is not your grain. Why are you blocking the ports? You should let the grain out,'" the official said.
A U.S. State Department official later said Blinken had told the meeting that, if the G20 was to remain relevant, it must hold Russia accountable for its actions in Ukraine.
Since starting what it calls a special operation to demilitarize Ukraine, Russia has bombed cities to rubble, thousands have been killed, and millions displaced.
Ukraine and its Western allies say Russia is engaged in an unprovoked land grab.
Russian forces have seized a big chunk of territory across Ukraine's southern flank and are waging a war of attrition in the Donbas, the eastern industrial heartland made up of Luhansk and Donetsk provinces.
Luhansk's governor said Russian forces were indiscriminately shelling populated areas on Friday.
"They are not stopped even by the fact that civilians remain there, dying in houses and yards," Serhiy Gaidai he said.
Reuters could not independently verify battlefield accounts.