UK bank Barclays said in a federal court filing on Monday that staff falsified documents to facilitate circumvention of US trade sanctions.

The bank agreed to pay $298m to US authorities to settle investigations relating to payments that the bank facilitated to countries facing government sanctions, including  Cuba, Libya, Iran, Sudan and Burma.

The filing said Barclays "accepts and acknowledges responsibility for its conduct and that of its employees." US officials said the bank altered payment messages or deleted information about sanctioned countries. In other cases, Barclays returned payments out of fear they would be discovered by US officials, sending fax cover sheets that said: "Payments to U.S.A. must NOT contain the word listed below." Prosecutors said payments often were re-sent after the reference to the sanctioned country was omitted.

Prosecutors also said that in an internal manual, Barclays included instructions for processing payments to the US from foreign banks to avoid detection. Payments going to the New York branch were filtered before they left Britain to prevent "the seizure of funds in the USA," according to an employee email cited in a federal-court filing.

In one email referenced by prosecutors, an employee wrote about how to avoid detection: "A good example is Cuba which the US says we shouldn't do business with but we do."

The Obama Administration is currently beefing up its sanctions regime against Iran and last May, ABN Amro agreed a $500m fine to settle claims that it helped Iran, Libya, Sudan and Cuba evade US sanctions by "stripping" the identities of transactions to conceal the countries from which they originated. Last December, Credit Suisse paid $536m for sanctions busting and in early 2009, a subsidiary of the UK's Lloyds Banking Group paid $350m also relating to circumvention of sanctions.

This week, Stuart Levey, the Under Secretary for Terrorism and Financial Intelligence within the United States Department of the Treasury, is visiting is financial centres in Lebanon, Bahrain and the United Arab Emirates - - all three countries host subsidiaries of Iranian banks - - to win support or warn of the penalties for defying US sanctions against Iran.

Levey said in the Financial Times on Monday that the latest round of measures also sharpens the focus on another sector that is a critical lifeline for Iran’s proliferation and evasion: shipping. He said some of Iran’s most dangerous cargo continues to come and go from Iran’s ports, "so we must redouble our vigilance over both their domestic shipping lines, and attempts to use third-country shippers and freight forwarders for illicit cargo."