Choosing when to welcome a pariah state back into the international fold is fraught with risk. The ill-judged rehabilitation of Muammar Gaddafi in 2003 merely reinforced a despot. But Barack Obama has made the right decision to open the door to Myanmar with his historic presidential visit.

Human rights groups have attacked the US president for rushing to legitimise Myanmar’s nominally civilian government before democratic reforms take root. Thein Sein, the reform-minded president, has released hundreds of prisoners, ended media censorship and allowed democracy activist Aung San Suu Kyi’s National League for Democracy to enter parliament. But the government’s ambivalence in the face of what look increasingly like anti-Muslim pogroms in Rakhine state shows that human rights are far from entrenched. Many political prisoners also remain in jail, although 60 were set to be freed last night.

It is just for these reasons that the trip is well-timed. It has already prompted a raft of new initiatives on the eve of his arrival. But for reform to continue, Mr Thein Sein needs to show the old guard concrete results. Many still exercise influence in parliament and the government. There is frustration that the US has suspended rather than lifted sanctions. The first visit by a sitting US president is a very public signal that support will be forthcoming if the pace is kept up.