Mr Obama has attended two previous US-EU summits
The European Union has scrapped a summit with the US, after President Barack Obama decided not to attend.
The event in Madrid in May was to have been the highlight of Spain's six-month EU presidency, and the cancellation is seen as a humiliating blow.
Officials say the summit may take place later this year.
BBC European affairs correspondent Oana Lungescu says many see Mr Obama's decision as a snub to the EU's hopes of boosting its global role.
On Tuesday, the White House said Mr Obama had had no plans to attend the event, and aides pointed out he had visited Europe six times in 2009.
Mr Obama attended US-EU summits in Prague and Washington last year.
A Spanish official quoted by AP news agency said Madrid had assumed Mr Obama would be attending the event.
In fact, Spain only found out about Mr Obama's decision through the press.
For the EU, it is a serious setback, says the BBC's European affairs correspondent.
It would have been the first major summit since a new council president and foreign policy chief were appointed to ensure that the bloc of 27 countries speaks with one voice.
In Washington, US National Security Council spokesman Mike Hammer said the American president was "committed to a strong US-EU partnership and with Europe in general".
An EU official played down the snub, arguing that president Obama had urgent issues to deal with at home.
But in Brussels there is growing concern that President Obama is taking Europe for granted and focusing instead on China and Russia, our correspondent says.