The first formal US-Russia summit between Barack Obama and Dmitry Medvedev was never expected to sign off on new deals of great substance. Even the easiest issue – agreeing on a new round of nuclear arms cuts – will still take months of careful negotiation to pin down. It could yet be derailed by disagreement over the building of a US ballistic missile defence system. But this week’s meetings in Moscow will have succeeded if they change the tone of mutual recrimination in a vital bilateral relationship.

The commitment of both sides to reduce their nuclear warheads and launch vehicles by a third in a new treaty is very welcome. Perhaps they could have been more ambitious, but it should lay the foundation for further progress.