Britain has asked for a "technical hold" to be placed on a U.S. proposal to add Abshir Abdillahi and Mohamed Abdi Garaad to the list of people subject to sanctions under U.N. Security Council Resolution 1844, Britain's Foreign Office said.
The "technical hold", requested in April and in effect indefinitely, gives the British government time to look into the legal implications of implementing the measures.
Security Council Resolution 1844 imposes a travel ban and an asset freeze on people who "engage in or provide support for acts that threaten the peace, security or stability of Somalia".
The U.S. proposal marks the first time that alleged pirates would be targeted by the sanctions, throwing up legal questions for Britain.
Pirates from Somalia, which is battling an Islamist insurgency, have made tens of millions of dollars in ransoms for the release of ships and crews seized in the Indian Ocean and Gulf of Aden.
Britain does not condone the payment of ransoms and supports strong action against known pirates, the Foreign Office said.
However, it is not illegal under British law to pay ransom and if the two alleged pirate commanders were added to the list, it could create a legal conflict for British-based companies by outlawing ransom payments that ended up in the hands of the two suspects, a British government source said.
The move could throw "UK companies open to prosecution," the source said, adding that the issue created a "difficult balancing act" between cracking down on piracy and the shipping industry's commercial interests.
A number of options were being considered for resolving the problem, the source said without elaborating.
The Financial Times reported on Monday that the proposed sanctions would affect law firms, insurers and private security companies in London that arrange ransoms to release kidnapped ships and crews.
The Gulf of Mexico oil spill from British-based BP's Macondo well and U.S. concern over the release last year of the Lockerbie bomber to Libya have caused strains between the United States and Britain's three-month-old coalition government.
