The announcement that the US will resume formal contacts with Egypt's Muslim Brotherhood may dismay Israel. But it is a vital acknowledgement of the new political realities in the Arab world's most important country – a move that changes little in practice, but a great deal in principle.

Whatever one's view of the Brotherhood, founded in 1928 and the doyen of the Islamist groups in the Middle East, it is far and away the best organised of the parties that will compete in the all-important elections for a national parliament and president, scheduled to be held before the end of the year. Inevitably, it will be deeply involved in shaping a new and more democratic constitution.

Naturally, the Brotherhood's conservative and deeply Islamic vision of the state, and its ambivalent attitude to the rights of women and other minorities, arouse concerns. There are understandable suspicions, too, about the sincerity of its commitment to non-violent means. But it was not considered a terrorist group by the US State Department – and although it was repressed by a succession of Egyptian rulers, Hosni Mubarak did allow a few of its representatives to sit in the old rubber-stamp parliament as independents, with whom US diplomats were permitted to have contact, and thus keep lines of communication open. It would have been absurd if those contacts were not broadened now, as Egypt gropes towards a democratic future. Far too often in the past, Washington has complicated its task in the Middle East by refusing to recognise realities on the ground.

However, this will not be to the liking of Israel, nor that of the powerful US pro-Israel lobby (an important consideration as election season approaches). The Brotherhood, it will be pointed out, does not recognise Israel, and has close ties to Hamas, the Gaza-based Palestinian group that denies the Jewish state's right to exist. For the US to have formal dealings with the Brotherhood will therefore only complicate the Obama administration's fraught relations with the government of Benjamin Netanyahu. But sooner or later, Israel must also accept the reality of what is happening in its most important neighbour.