WASHINGTON - The Obama administration is open to the idea of a short-term extension of the housing tax credit but wants to see it remain focused on first-time home buyers, senior White House aide Lawrence Summers said on Wednesday.

It does seem to me that concentrating on first-time home buyers has the virtue that you're stimulating demand without also stimulating supply as distinct from (providing) the credit to those who are turning over a home, Summers told Reuters in an interview.

Summers said that in weighing whether an extension of the credit could benefit the economy, the White House would also take into consideration its impact on the deficit.

He said there was a case to be made for extending the credit in terms of supporting the housing market. But he added: At the same time, we can't afford everything for which there is a case.

Summers also said the administration would look at the possibility of expanding the size of the credit, but on that issue the impact on the deficit would be a consideration.

(Reporting by Jeff Mason, Caren Bohan and Simon Denyer)