The US lobbied Russia this year on behalf of Visa and MasterCard to try to ensure the payment card companies were not "adversely affected" by new legislation, according to American diplomats in Moscow.

A state department cable released this afternoon by WikiLeaks reveals that US diplomats intervened to try to amend a draft law going through Russia's duma, or lower house of parliament. Their explicit aim was to ensure the new law did not "disadvantage" the two US companies, the cable states.

The revelation comes a day after Visa – apparently acting under intense pressure from Washington – announced it was suspending all payments to WikiLeaks, the whistle-blowing website. Visa was following MasterCard, PayPal and Amazon, all of which have severed ties with the site and its founder, Julian Assange, in the past few days.

The companies have justified their decision to stop donations on the grounds that WikiLeaks is acting "illegally". Each has quickly become the target of sustained online revenge attacks by disgruntled hackers, with mastercard.com paralysed today.

The cable, dated 1 February 2010, states that the Obama administration took up the companies' plightcause with senior Russian government officials. Earlier this year Moscow unveiled plans to create a new National Payment Card System (NPCS) that would collect all credit card fees on domestic transactions – depriving Visa and MasterCard of revenue.

A consortium of state-owned Russian banks would administer the system and collect processing fees "estimated at $4bn (£2.53bn) a year", the cable claims. Additionally, sending payment data abroad would be forbidden under the law going through Russia's rubberstamp lower house of parliament – another potential blow to the US credit card companies.

The Russian media reported this week that the objections of Visa and MasterCard had now been "allayed". The head of Russia's finance ministry, Sergei Barsukov, said the law had been "re-worked" to take into account the concerns of "foreign operators". There would be no extra restrictions on foreign money transfers, he promised, with transactions taking place in a "simple format".In the cable Matthias Mitman, a US diplomat specialising in economic affairs, and based at the Moscow embassy, urged Obama's presidential commission on Russia to take up the issue. Obama agreed to found a new bilateral commission with the Russian president, Dmitry Medvedev, as part of the reset in US-Russian relations.

Mitman comments: "This draft law continues to disadvantage US payment card market leaders Visa and MasterCard, whether they join the NPCS or not. If they join, the NPCS operator will collect the fees, leaving them to collect processing fees only when card-holders travel abroad – a tiny section of the market.

"If they do not join but choose to compete with NPCS cards, they will have to set up payment processing centres in Russia, a very large investment in itself, and compete against a system likely backed by the largest Russian state banks."

The answer, Mitman suggests, is for the Obama administration to actively bat for Visa and MasterCard. "While the draft legislation has yet to be submitted to the duma and can still be amended, post will continue to raise our concerns with senior GOR officials.

"We recommend that senior USG officials also take advantage of meetings with their Russian counterparts, including through the Bilateral Presidential Commission, to press the GOR to change the draft text to ensure U.S. payment companies are not adversely affected."

Russia's duma is due to hold a first reading of the new law on Friday. President Dmitry Medvedev asked officials last December to modernise Russia's electronic payment system and come up with a home-grown version of the western model.

Visa said: "Russia is an important market for Visa. The company remains committed to continue engaging constructively with all government and private sector stakeholders to support the development of the electronic payments industry in Russia. Visa supports the creation of a regulatory framework which actively promotes competition and transparency, ensures consumer choice and robust consumer protection, provides data security and further integrates Russia into the global financial and payment system''.

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