In her first address to the United Nations in more than 50 years, Queen Elizabeth II specified terrorism and climate change as new challenges that have emerged to test the institution.
"Careful account must be taken of the risks faced by smaller, more vulnerable nations," many of them from the United Kingdom, Elizabeth said, as queen of 16 U.N. member states and head of the Commonwealth of 54 countries - many of which are islands - with a population of nearly 2 billion people.
The 84-year-old British monarch last visited the United Nations in 1957. That was four years after she was crowned queen.
The queen noted several times throughout her address how much progress the international body has made since she last visited the international body.
"You have offered humanitarian assistance to millions of people affected by natural disasters and other emergencies," Elizabeth said. "And you have been deeply committed to tackling the effects of poverty in many parts of the world. But so much remains to be done."
Read her prepared remarks
NYC Anglophiles Aflutter Ahead of Queen's Visit
So much has changed since Elizabeth's last visit to New York, CBS News Correspondent Jim Axelrod reports. Must-see for the queen during her first tour of North America was the Empire State Building. Now it's a factory in Canada that manufactures the BlackBerry.
Elizabeth challenged the United Nations to spearhead the international response to global dangers and promote prosperity and dignity for all the world's inhabitants.
"In my lifetime, the United Nations has moved from being a high-minded aspiration to being a real force for common good," the British monarch told diplomats. "That of itself has been a signal achievement. But we are not here to reminisce. In tomorrow's world, we must all work together as hard as ever if we are truly to be United Nations."
The queen was well-received at the U.N., CBS News Foreign Affairs Analyst Pamela Falk reports. The U.N. delegations were pleased to hear their work in peacekeeping applauded in what is likely to be considered a legacy speech of Elizabeth's 60-year reign, Falk reports.
Security at the United Nations is as tight as it has been for President Obama, Falk reports from U.N. Headquarters.
"Responding to international doubts about the relevance of the British monarchy, the queen held a regal show at United Nations Headquarters in New York," said Falk. "With Scotland Yard inside the U.N., royal mounted horses outside and tight security to guard her, she walked down the aisle through the delegations to the podium to continuous applause from the 192 nations attending."
Elizabeth also praised the U.N.'s aims and values which have endured - promoting peace, security and justice, fighting hunger, poverty and disease and protecting the rights and liberties of every citizen.
"For over six decades the United Nations has helped to shape the international response to global dangers," the queen said. "The challenge now is to continue to show this clear ... leadership while not losing sight of your ongoing work to secure the security, prosperity and dignity of our fellow human beings."
Elizabeth and her husband, Prince Philip, flew to New York from Canada for a five-hour visit that included stops at the Ground Zero site where the twin World Trade Center towers were destroyed on Sept. 11, 2001. She laid a wreath in tribute to the thousands who died, and then officially opened the British Memorial Garden honoring the 67 Britons who lost their lives that day.
Dressed in a two-piece white, blue and beige dress with a ruffled hem and a matching brimmed champagne-colored silk hat with flowers, the queen was greeted on her arrival by U.N. Secretary-General Ban Ki-moon and General Assembly President Ali Abdessalam Treki and their wives.
After posing for photos in front of U.N. flags, she went to the memorial to UN peacekeepers and staff members killed in the line of duty and laid a wreath before the tattered UN flag that flew over U.N. headquarters in Baghdad on Aug. 19, 2003, when the building was bombed, killing top U.N. envoy Sergio Vieira de Mello and 21 others.
The queen walked slowly into the two-thirds full chamber, as past diplomats gave her a standing ovation. Before her speech she sat in a beige leather chair where she spent a half-minute fishing her reading glasses out of her black handbag, resealing the clasp and laying her speech out on her lap, tasks made harder because of her white gloves.
She looked up to occasionally peer out at the crowd, where the visitor and press upper galleries were full, scanning left and right and then looking intently straight forward. Her hands lay quietly on her speech.
The queen recalled that when she came to the United Nations in 1957, there were just three U.N. operations overseas.
"Now, over 120,000 men and women are deployed in 26 missions across the world," she said. "You have helped to reduce conflict."
At the end of the short speech, she was loudly applauded.
"Everyone was very impressed," Russia's deputy U.N. ambassador Konstantin Dolgov told AP. "She's a big part of the United Nations, very important."