Singer Cliff Richard may be forced to miss his annual trip to the US for the Open Tennis after allegations of sexual assault.

The 73-year-old may not be allowed to enter US while police investigate allegations that he sexually assaulted a young boy at an event in 1985, reports femalefirst.co.uk.

"You would be mad to try to get on a plane if you had a child abuse inquiry hanging over you," a source was quoted by The Sun newspaper as saying.

However, people who have been questioned under caution by police can apply to the US Embassy for special consideration for a visa and will be assessed on an individual basis.

The US Embassy in London said: "We do not comment on individuals."

The "Summer Holiday" hitmaker's property in Berkshire, South East England, was recently searched and items were taken away for investigation after the allegations came to light Thursday.

Richard, who was residing at his home in Portugal at the time, has denied the allegations but admits he's been aware of them for a "while."

He has not been arrested and is yet to be questioned by police.