The inauguration of a new president in Iran opens a window for change, if he and Iran's other leaders want it. But such windows can close quickly.
Cautious regional welcome awaits Iran's president
Tomorrow, for the first time in eight years, Iran will have a new president, one apparently more willing to engage with the world than his belligerent predecessor.
There is a curious parallel with the first presidency of Barack Obama. In 2009, when Mr Obama made his inaugural address, he did so as a man welcomed as a breath of fresh air after the aggressive years of George W Bush. The promise Mr Obama addressed to Iran in that speech - "We will extend a hand if you are willing to unclench your fist" - could serve to express the precise view of the Arabian Peninsula countries about Iran at present, on the occasion of the inauguration of Hassan Rouhani.
It is no secret that relations between Iran and the countries on this side of the Gulf have been difficult. Indeed, Iran's relationship with the entire region has been fraught this past decade.
The reason is to be found in Iran's ambitions and how they are pursued. Iran is a big country, a vitally important neighbour and a growing regional power. Yet it is has not been led responsibly.
In this region, Iran's involvement has often been negative. In Iraq, it has meddled to serve its own narrow interests rather than those of the wider Iraqi population. In Syria, its alliance with the violent regime of Bashar Al Assad has prolonged the agony of ordinary Syrians. In Yemen and in Lebanon, the hand of Iranian intelligence can be detected in discord and strife.
The UAE, meanwhile, has offered the hand of civility: this country's leaders want to resolve Iran's occupation of the three islands near the Strait of Hormuz diplomatically - and yet the outgoing president of Iran, Mahmoud Ahmadinejad, provocatively visited them last year.
Iran's controversial nuclear programme, though overblown by the US and Israel, also reflects Tehran's ambition. The Arab world wants to see Iran come back into the region and the world, and hopes at this juncture to see a new transparency on the nuclear issue, and well-intentioned diplomacy on other matters.
The inauguration of Mr Rouhani gives Iran a window of opportunity. If he and Iran's other leaders wants to mend fences with neighbours across the Gulf, they will find a fair hearing. But such windows close rapidly.
A responsible, secure and prosperous Iran is in everyone's interest. The Iranian people want it and the peoples of the Middle East want it. If Mr Rouhani unclenches Iran's fist, he will find many friends on this side of the Gulf willing to extend their hands.