A deepening economic standoff between Russia and the west over the future of Ukraine has rippled through trading floors and boardrooms with exporters scrambling to protect revenues and global financial firms halting services.   

US President Barack Obama's threat to target major sections of the Russian economy should President Vladimir Putin follow-up his annexation of Crimea with further incursions in Ukraine has caused alarm across Europe.   

Denmark's foreign ministry held a special briefing for about 130 companies, including drugs firm Novo Nordisk and brewer Carlsberg, after being inundated with inquiries about the business implications of the crisis.

In an email to Reuters, Carlsberg's chief executive said he was monitoring the situation closely and would act if sanctions had a direct impact on his drinks group's business. The company produces and sells local beers in both Ukraine and Russia.   

"Until now it has been business as usual. We produce, sell and distribute our products to the market without problems," said CEO Jorgen Buhl Rasmussen. "Our focus is on our employees and our breweries."

Lemken, a German manufacturer of ploughs and other farm machinery, has seen a big drop off in orders from Russia, its second-biggest export market after France, in recent weeks as a sliding rouble raises their sale price.

With Moscow vowing to retaliate against the west's sanctions, Anthony van der Ley, managing director of the family-run business, is taking no chances. He is sending machinery to Russia now in case the border closes or import charges are hiked. 

"We're sending the machines specially made for Russia to Russia and we are leaving the machines that we can sell in other countries here due to the risk."  

Profine, a plastic window frame manufacturer with annual revenues of €700m, has so far managed to compensate for the rouble slide by increasing sales but won't be able to do that forever.

"If there are further sanctions, that would be poison for the economic development of our partners," said Peter Mrosik, the German firm's managing partner.

President Obama unveiled sanctions against members of President Putin's inner circle on Thursday as well as against Bank Rossiya, partly owned by a Putin ally.

In response, Visa and MasterCard stopped providing services for clients at Rossiya and another bank SMP, whose co-owners, two brothers, are also on Mr Obama's list.       

SMP described the move by Visa and MasterCard as unlawful. However, financial services firms are wary of doing business with any person or group that can be linked back to the targets.

Banks have paid dearly in the past for violating US sanctions on countries such as Iran.    

What bankers and business people fear is an escalation of measures that would choke off international payments and trade, halt investments and stymie deals.

Germany's main trade body warned that full-blown economic sanctions would be a "real catastrophe".

In a worst-case scenario, Washington would stop banks doing business with Russian counterparts and corporates, similar to the sort of sanctions that were imposed on Iran.

Germany's "wise men" council of economic advisers said this week that the Ukraine crisis was the biggest threat to growth globally, and especially in Germany, because of Russia's importance as an energy exporter. 

"What has been announced so far is really nothing. It is purely cosmetic," said a French banker based in Moscow.

"The biggest risk is tougher sanctions and really the potential impossibility of transfers in US dollars. That will hit trade finance, which depends on correspondent accounts in dollars," said the banker, who declined to be named.

"Being able to make payments in dollars is crucial for the Russian economy, which is dependent on energy exports. It would really hurt us domestically."

State-owned Russian banks and companies are expected to repatriate funds from overseas after Putin told them this week to bring their assets home.

But foreign bankers in Russia said things would have to deteriorate further before they would reconsider their investments there.   

"It would have to be a lot worse than this. We are waiting for the response from the Russian side. It's very difficult to predict," said another western banker in Moscow.

"I haven't heard of any western companies pulling out of Russia. If a company is substantially invested here it will be difficult for them to consider getting out."

Even before the Crimean crisis blew up last month international banks such as HSBC, Credit Suisse and Barclays had pulled out of dozens of markets because the risk of falling foul of financial crime rules and sanctions outweighed the returns.  

The cost to banks of cleaning up an array of misdeeds that have come to light since the global financial crisis has soared to over $100bn.       

With that figure expected to climb, western banks have so far steered clear of attempts by Iran to get them involved in financing humanitarian transactions, despite a diplomatic thaw.     

Since the US and European sanctions so far focused on wealthy individuals close to President Putin, private banks which cater to powerful Russians are under the spotlight.         

Switzerland, the global hub for private banking and a bolt-hole for wealthy Russians, has yet to impose any restrictions but its banks, such as UBS and Credit Suisse, still have to be aware of sanctions when they deal with clients.        

Vasili Brokvo, the head of communications for Russia's state defence conglomerate Rostec, made the corporate case for peace.   

"We hope and our international partners also hope that political differences over certain issues won't annul or destroy everything we've built and all previous agreements with foreign partners will be successfully implemented," he said on a business trip to Chile this week.