Mr Kennedy is fighting cancer
Conservative politicians have criticised the decision to grant an honorary knighthood to the veteran US Senator Edward Kennedy.
The honour was granted to the 77-year-old for services to the US-UK relationship and to Northern Ireland.
However, the DUP's Diane Dodds welcomed Mr Kennedy's decision to accept the honour.
She said it was "an example of how the nationalist campaign for a United Ireland has failed".
"Although American law forbids the use of titles bestowed by non-American heads of state, I wish to congratulate Sir Edward Kennedy on receiving his award from our Head of State.
"If someone like Edward Kennedy, with his long history of supporting Irish nationalist causes is content to be the recipient of one of the highest honours which our Queen can bestow it sets a remarkable example to others within broader nationalism."
Rhode Island Congressman Patrick Kennedy, the Senator's son, told the Boston Globe newspaper that his father had joked to him, "I hope the Irish don't get angry with me for accepting it."
A member of the Irish-American political dynasty, Mr Kennedy played a high-profile role in the Northern Ireland peace process.
He refused to meet Sinn Fein leader Gerry Adams during the latter's St Patrick's Day trip to the US in 2005 following the murder of Robert McCartney.
Former Conservative minister Lord Tebbit, whose wife was badly injured in the 1984 IRA Brighton bombing, said Senator Kennedy was biased towards the republican movement.
"I'm not sure Her Majesty would be entirely comfortable with it, but then it's the prime minister who decides these things," he told BBC Radio Ulster.
"I don't think Kennedy would have got past the honours committee in view of his personal life in the US, let alone his entirely one-sided partisan attitude to British politics."
Irish Senator David Norris said it was "impertinent" of Lord Tebbit to presume to speak for the Queen.
"He has been a moderating force and a decent man in American politics. He's on the side of the downtrodden - maybe that's what Tebbit doesn't like," he said.
Martin O'Muilleoir of the Belfast Media Group said Senator Kennedy was a "giant of Irish-America".
"It is true that across nationalist Ireland and Irish-America there are a lot of people who would not want to accept a knighthood," he said.
"You have to remember that in the States in particular in recent years, it has been more acceptable for leading figures in Irish-American to accept these gongs."
The award was formally announced in Washington by Gordon Brown during his address to both houses of Congress.
Edward Kennedy, flanked by David Trimble and John Hume in 1999
In his address Mr Brown said: "I hope that you will allow me to single out for special mention today one of your most distinguished senators, known in every continent and a great friend.
"Northern Ireland is today at peace, more Americans have health care, more children around the world are going to school and for all those things we owe a great debt to the life and courage of Senator Edward Kennedy," he said.
The most senior living member of the famous Irish-American political dynasty, Mr Kennedy was diagnosed with brain cancer in May last year after being rushed to hospital with stroke-like symptoms.
He has since had chemotherapy and radiation to treat the malignant glioma, an aggressive type of brain tumour.