The Queen is shocked and saddened at the shootings on a college campus in Virginia, US, in which 33 people died, Buckingham Palace has said.
The shootings are the deadliest ever seen at a US school
The Queen and the Duke of Edinburgh are to pay a two-day visit to Virginia on 3 and 4 May as part of their first official US trip in 16 years.
They will mark the 400th anniversary of the English settlement at Jamestown.
UK Foreign Secretary Margaret Beckett has also extended her condolences to the families of those affected.
Speaking at the United Nations in New York, Mrs Beckett said: "Can I first say how appalled everyone is by the terrible news from Virginia.
"Our deepest sympathy and our condolences of course go to that community and to all of those whose families are directly affected."
The deadly attacks happened early on Monday morning at the Virginia Tech university in the town of Blacksburg.
As well as the 33 fatalities, about 15 people were hurt and the gunman, who has not yet been identified, also died.
The incident has claimed more lives than any other US school shooting tragedy.
The Home Office Minister, Tony McNulty, was a student at Virginia Tech in the 1980s and returned to visit the university around two weeks ago.
He told BBC Radio Five Live: "There is, as people know, a really deeply ingrained culture towards gun ownership in the States - Virginia as well as anywhere else.
"It just hasn't been - happily - matched here in anyway. But Blackburg and Virginia - these are very, very safe places. I had no difficulties at all while I was over there studying for about 18 months. "
He said he also felt "completely, completely safe" when he returned to give a lecture at the department where he studied.
"In that context, it's just a stark tragedy that really does chill you to the bone," he said.