David Cameron indicates asset freezes and travel bans will be imposed within days as tensions continue to escalate in Crimea

This article is more than 6 years old

This article is more than 6 years old

Western officials will meet in London on Tuesday to identify Russians who will be subject to asset freezes and travel bans that officials hope will persuade Moscow to withdraw its presence from Crimea.

The sanctions, which the British prime minister, David Cameron, indicated would be imposed within days, come as tensions escalate in the Crimean peninsula, where unidentified men reportedly fired warning shots as they moved into a Ukranian naval base on Monday.

In Washington, the White House gave its strongest indication yet that Russia is effectively being thrown out of the G8 group of industrialised nations on Monday, and insisted the world community would refuse to accept the results of a Crimean referendum later in the week.

Barack Obama's press secretary, Jay Carney, said: "It is hard to see the G8 [summit] happening", in Sochi in June.

Carney said a referendum in Crimea, scheduled for Sunday, "would not be legal under Ukraine's constitution and therefore would not be accepted by the United States and its international allies and partners".

There is concern in the US and Europe that Sunday's referendum could mark a dangerous turning point in the Ukraine crisis, enabling the Russian president, Vladimir Putin, to increase Russia's presence in the peninsula, claiming to be protecting Crimean's right to self-determination.

European foreign ministers are expected to make a final decision about sanctions next Monday – the day after the referendum.

Nato announced on Monday night it will deploy AWACS reconnaissance aircraft to overfly Poland and Romania as part of alliance efforts to monitor the crisis.

The flights "will enhance the alliance's situational awareness," a Nato official said, adding: "All AWACS reconnaissance flights will take place solely over Alliance territory."

The latest in a series of low-level confrontations involving pro-Russian forces and the Ukranian military in Crimeaon Monday involved 10 unidentified armed men who reportedly fired in the air at a Ukrainian naval post.

Ukraine's Channel 5 television quoted defence official Vladislav Seleznyov as saying the shooting took place at a motor pool base near Bakhchisaray. The men in two minibuses drove into the compound and demanded Ukrainian personnel there give them 10 trucks.

There have been several similar incidents in recent days, as Russian forces appear to be testing the resolve of Ukrainian forces in Crimea, avoiding the kind of confrontation that results in bloodshed.

The US and Europe are seeking to tighten the noose on Moscow with sanctions, while maintaining top-level discussions and insisting there is a way in which Putin can change course.

All G8 countries except Russia – a separate group commonly known as G7 – have previously announced suspension of preparatory meetings, but so far have held back from cancelling the summit itself.

"No one is preparing for the G8 right now because of the actions Russia has taken," Carney said on Monday. "We'll see how this transpires, but absent any preparation it hard to see the G8 happening."

If the G8 summit is cancelled in June, or hosted in a different country, it would effectively mean Putin had been thrown out of the club of powerful world leaders.

The US is planning to use a visit to Washington on Wednesday by Ukraine's prime minister, Arseniy Yatsenyuk, to shore up the legitimacy of Kiev's nascent government. Yatsenyuk will also give an address to the United Nations in New York.

In Washington, there have been questions over whether Britain and Germany are committed to holding Putin to account given both countries' economic ties with Russia. Europe is viewed to be particularly hampered by its reliance on Russian gas.

Carney also played down reports that Moscow could restrict gas exports to Ukraine or other parts of Europe in a retaliation against US-led sanctions.

European leaders have been rapidly exploring ways in which they could counteract any such move by Putin, including reversing the flow of gas in pipelines in the continent, pumping supplies into Ukraine from western Europe.

"European gas inventories are way above normal levels due to a milder than usual winter in Europe, and could replace a loss of Russian exports for several months, if necessary," Carney said.

But he added any move to starve Europe of gas would by a "lose-lose situation for everyone, most particularly for Russia".

"Russia has a substantial financial interest in maintaining those exports," Carney said.