By Richard Lister
BBC News, Washington
Mr Obama's position on the Middle East differs little from President Bush's
"There is one president at a time."
That is the mantra from the Obama transition team whenever it is confronted with an issue on which it would rather not comment.
It annoys senior Democrats like Representative Barney Frank, who said "that seriously overstates the number of presidents we have".
And Mr Obama's refusal to make any substantive comment on the situation in Gaza has also threatened to lose him support in the Arab world.
But the US constitution makes it pretty clear who is in charge at the moment and until 20 January, that person is George W Bush.
Mr Obama does not have the legal authority to back his words with actions; he does not have an administration in place and he risks complicating what has otherwise been a smooth transition process if he decides to take on the presidential mantle before he is sworn in.
Yet it is not quite as simple as that, of course.
There is a power vacuum in Washington at the moment - as there always is in the waning weeks of any administration.
But so profound is this one that the Obama team decided to raise the president-elect's profile in the weeks after his election.
He reassured financial markets that he was working behind the scenes on a far-reaching economic stimulus package.
When Mr Obama arrived in Washington, his first appointment was with the House Speaker, Nancy Pelosi, because as he said "the business of the people cannot wait".
He has made statements on the economy, the carmakers' bail-out, and the attacks in Mumbai - so why so little on Gaza?
Well, with the exception of Mumbai, he has spoken only about domestic issues - seen as fair game for an incoming president.
The attacks in India were far more clear-cut than the turmoil in Gaza.
They were an unusual event which presented no lingering policy issues and required no continuing diplomacy.
And that is key.
Mr Obama has reiterated that it is President Bush who is responsible for American diplomacy.
"When it comes to foreign affairs it is particularly important to adhere to the principle of one president at a time," he said.
"There are delicate negotiations taking place right now and we can't have two voices coming out of the United States when you have so much at stake."
Gaza is a political minefield for Mr Obama.
If he makes a statement that suggests he would pursue a different Middle East policy from that of the Bush team, it would pull the rug from under the current administration's diplomatic efforts in the region.
It would also cost him Republican goodwill at home if he were to undermine President Bush in that way.
If he issues a statement which puts him in lock step with the Bush team's approach, then he loses flexibility when the issue arrives in his in-tray in two weeks time.
Whatever he says now will be regarded as policy, but the political landscape in the Middle East could be quite different when he is sworn in.
It may be that events on the ground create overwhelming pressure on Mr Obama to make a more substantive statement.
If so, he will have to weigh up the diplomatic and political damage done by saying little, against the damage done by saying something which will inevitably be condemned by one of the players in the region - and could come back to haunt him.
In fact, nothing he has said on the Middle East in the past has been significantly out of step with President Bush's policies.
Visiting the Israeli town of Sderot in July, he suggested that he too would respond if rockets were being fired at his house.
He has also spoken about the problem of negotiating with Hamas when it is "not representative of a nation state, does not recognise [Israel's] right to exist, has consistently used terror as a weapon and is deeply influenced by other countries".
However, he has always been careful to avoid definitive statements which lock him into a particular course of action.
All recent presidents have made some kind of policy shift in their efforts to find peace in the Middle East - President Bush was the first to call openly for a two-state solution, for example.
But there is very little political advantage for Barack Obama in revealing his hand before he sits at the table for real.