If postponement of this week's trade talks between the US and the United Arab Emirates were the only side effect of Dubai Ports World's decision to divest its American container terminals, we could draw a line under the controversy. But that would almost certainly be wrong.

Although DP World wisely avoided recriminations when it said on Friday it would sell its US port assets, there is a deeper mood of protectionism on Capitol Hill. Facing a tough battle for re-election in November, members of Congress have submitted plans to toughen up scrutiny of foreign ownership, the worst of which would debar foreign investment in US "critical infrastructure" on grounds of security. This could include major utilities and the container terminal operations at US ports, more than three-quarters of which are under foreign management.