Beyonce has owned up and admitted that she did lip-sync her performance of the U.S. national anthem at the inauguration of President Barack Obama.

She says she simply did not have time to rehearse with the band or do a proper sound check.

The singer insists she will be live at the Superbowl half-time show this weekend.

The half-time performance by Madonna last year was the most-watched Super Bowl show ever, with roughly 114 million viewers.

Beyonce opened a news conference on Thursday by belting out The Star-Spangled Banner - as if to leave no doubt of her capabilities.

But she says the inauguration was too important.