The US is exploring legislation to further isolate Russia from the global economy, including banning the import of its oil and energy products into the country.
The price of oil jumped more than 10 dollars (£7.5) a barrel on Monday as the conflict in Ukraine deepened amid mounting calls for harsher sanctions against Russia.
In a letter to Democrats released on Sunday night, House of Representatives speaker Nancy Pelosi said the legislation under consideration would also repeal normal trade relations with Russia and Belarus and begin the process of denying Russia access to the World Trade Organisation.
Ms Pelosi said the House would also empower the Biden administration to raise tariffs on Russian imports.
The US Congress intends to approve the Biden administration’s request for 10 billion dollars (£7.5) in humanitarian, military and economic support for Ukraine as part of omnibus government funding legislation this week, she added.
Brent crude oil briefly surged over 10 dollars (£7.5) to nearly 130 dollars (£98) a barrel early on Monday. Benchmark US crude was up nearly nine dollars(£6.8) at more than 124 dollars (£93) a barrel.
The surge followed the failure of temporary cease-fires in two Ukrainian cities failed on Sunday, for which both sides blamed each other.
Russian forces intensified shelling of cities in Ukraine’s centre, north and south, a Ukrainian official said, upending attempts to evacuate besieged civilians.
Russia has said another ceasefire would start on Monday morning with the opening of humanitarian corridors in several areas, including Kyiv, Mariupol, Kharkiv and Sumy.
With the Ukrainian leader urging his people to fight in the streets, Russian President Vladimir Putin shifted blame for the invasion, saying Moscow’s attacks could be halted “only if Kyiv ceases hostilities”.
The outskirts of Kyiv, Chernihiv in the north, Mykolaiv in the south, and Kharkiv, the country’s second-largest city, faced stepped-up shelling late on Sunday, presidential adviser Oleksiy Arestovich said. Heavy artillery hit residential areas in Kharkiv and shelling damaged a television tower, according to local officials.
“This is likely to represent an effort to break Ukrainian morale,” the UK Ministry of Defence said of Russian tactics as the war entered its 12th day Monday.
Fighting has caused 1.5 million people to flee the country, which the head of the UN refugee agency called “the fastest-growing refugee crisis in Europe since World War II”.
Russia has made significant advances in southern Ukraine and along the coast, but many of its efforts have become stalled, including an immense military convoy that has been almost motionless for days north of Kyiv.
Food, water, medicine and almost all other supplies were in desperately short supply in the southern port city of Mariupol, where Russian and Ukrainian forces had agreed to an 11-hour cease-fire that would allow civilians and the wounded to be evacuated. But Russian attacks quickly closed the humanitarian corridor, Ukrainian officials said.
“There can be no ‘green corridors’ because only the sick brain of the Russians decides when to start shooting and at whom,“ Interior Ministry adviser Anton Gerashchenko said on Telegram.
A third round of talks between Russian and Ukrainian leaders is planned for Monday.
Ukrainian President Volodymyr Zelensky rallied his people to remain defiant, especially those in cities occupied by Russians.
“You should take to the streets! You should fight!” he said on Saturday on Ukrainian television. “It is necessary to go out and drive this evil out of our cities, from our land.”
Mr Zelensky also asked the United States and Nato countries to send more warplanes to Ukraine. But that idea is complicated by questions about how to provide aircraft to Ukrainian pilots.
He later urged the West to tighten its sanctions on Russia, saying that “the audacity of the aggressor is a clear signal” that existing sanctions are not enough.
A senior US defence official said on Sunday that about 95% of the Russian forces that had been arrayed around Ukraine are now inside the country. The official said Russian forces continue to advance in an attempt to isolate Kyiv, Kharkhiv and Chernihiv, but are being met with strong Ukrainian resistance.
The official, who spoke to the Associated Press on the condition of anonymity, said the convoy outside Kyiv continues to be stalled.
As he has often done, Mr Putin blamed Ukraine for the war, telling Turkish President Recep Tayyip Erdogan on Sunday that Kyiv needed to stop all hostilities and fulfil “the well-known demands of Russia”.
The Russian Defence Ministry on Sunday announced that its forces intend to strike Ukraine’s military-industrial complex with what it said were precision weapons. A ministry spokesman, Igor Konashenkov, claimed in a statement carried by the state news agency Tass that Ukrainian personnel were being forced to repair damaged military equipment so that it could be sent back into action.
Mr Zelensky criticised Western leaders for not responding to Russia’s latest threat.
“I didn’t hear even a single world leader react to this,” Mr Zelensky said on Sunday evening.
The Russian Defence Ministry also alleged, without providing evidence, that Ukrainian forces are plotting to blow up an experimental nuclear reactor in Kharkiv and to blame it on a Russian missile strike.
Mr Putin and French President Emmanuel Macron spoke on Sunday about the nuclear situation in Ukraine, which has 15 nuclear reactors at four power plants and was the scene of the 1986 Chernobyl nuclear disaster.
The men agreed in principle to a “dialogue” involving Russia, Ukraine and the UN’s atomic watchdog, according to a French official who spoke on condition of anonymity, in line with the presidency’s practices. Potential talks on the issue are to be organised in the coming days, he said.
Mr Putin also blamed the fire last week at the Zaporizhzhia nuclear plant, which Ukrainian officials said was caused by Russian attackers, on a “provocation organized by Ukrainian radicals”.
International leaders, as well as Pope Francis, appealed to Mr Putin to negotiate.
The death toll remains unclear. The UN says it has confirmed just a few hundred civilian deaths but also warned that the number is a vast undercount.
About eight civilians were killed by Russian shelling in the town of Irpin, on the northwest outskirts of Kyiv, according to Mayor Oleksander Markyshin. The dead included a family.
Video footage showed a shell slamming into a city street, not far from a bridge used by people fleeing the fighting. A group of fighters could be seen trying to help the family.
The handful of residents who managed to flee Mariupol before the humanitarian corridor closed said the city of 430,000 had been devastated.
“We saw everything: houses burning, all the people sitting in basements,” said Yelena Zamay, who fled to one of the self-proclaimed republics in eastern Ukraine held by pro-Russian separatists. “No communication, no water, no gas, no light, no water. There was nothing.”
British military officials compared Russia’s tactics to those Moscow used in Chechnya and Syria, where surrounded cities were pulverised by airstrikes and artillery.