Argentina's President has demanded that Britain starts to "act more intelligently" and begin talks with her country over the sovereignty of the Falkland Islands.
Cristina Fernandez de Kirchner coincided her emotional speech to the United Nations with the 30th anniversary of the end of the war over the territory, which Argentina calls Las Malvinas.
Britain has controlled the archipelago since 1833 - except for 74 days of occupation in 1982 - but Argentina claims it inherited rights to them from Spain upon its declaration of independence in 1816.
Ms Fernandez said Argentina was opposed to another war but criticised the British Prime Minister's decision to mark the day by flying the Falklands flag over 10 Downing Street.
"I felt shame from far away for them because wars are not to be celebrated or commemorated," she said, highlighting the hundreds of deaths in the conflict.
She described Britain as "a bully" for abusing its power as a member of the UN Security Council and lying about the history of the islands.
"We're not asking for much," she told the UN's Decolonisation Committee. "We're just asking to talk. ... We're not asking anyone to say 'yes' the Malvinas are Argentina's."
She then sat stony-faced through speeches by two Falklands representatives, who complained about Argentina's "bullying" tactics.
Prime Minister David Cameron insisted, however, that he would not discuss sovereignty as long as the 3,000 people on the wind-swept islands want to remain under the British flag.
In a speech at the annual Falkland Islands Government reception, Mr Cameron vowed that Britain would fight off any "aggression from over the water".
"When it comes to the sovereignty of the Falkland Islands, there will be absolutely no negotiation," he said.
"This is not some game of global monopoly, with nations passing a territory between them. It's about the islanders determining their own future."
The leaders' comments came as people braved snow and strong winds in Port Stanley to mark the anniversary.
"The celebration of liberation is the most important event of the year," hotel owner Alex Olmedo said.
The festivities in Port Stanley, which was decorated with British and Falklands flags, were full of reflection and expectations for the planned referendum in 2013 on the political status of the oil-rich islands.
"This is an opportunity for Falkland Islanders to celebrate our continued freedom to live as we determine for ourselves and to look forward to a bright and confident future," resident Graham Didlick said.
Foreign Office minister Jeremy Browne, who attended the Port Stanley service, said Falklanders had a "fundamental right" to "decide their own destiny.
Ms Fernandez also held talks with UN leader Ban Ki-Moon who "reiterated that his good offices to resolve this dispute remain available if the parties are willing to engage", UN spokesman Martin Nesirky said.