US President Joe Biden has accused Russia of shamelessly violating core tenets of the United Nations Charter during an address to the UN General Assembly at its headquarters in New York.

He said Russian President Vladimir Putin had "made reckless nuclear threats" after his speech this morning ordering Russia's first military "mobilisation" since World War II.

Mr Putin warned that Moscow would respond with the might of all its vast arsenal if the West continued with what he called its "nuclear blackmail".

The US President said "no-one threatened Russia and no-one other than Russia sought conflict".

Russian forces have attacked Ukrainian schools, railway stations and hospitals, part of Moscow's aim of "extinguishing Ukraine's right to exist as a state," Mr Biden said.

He added that Russia is making "irresponsible threats" to use nuclear weapons.

Mr Biden told the UN gathering in New York: "A nuclear war cannot be won and must never be fought."

The US President said that his country's sanctions against Russia explicitly allow for food to be exported.

He said Russia is "pumping out lies" by trying to "pin the blame". for the global food crisis on the sanctions.

The United States supports expanding the UN Security Council, Mr Biden added.

Minister for Foreign Affairs Simon Coveney said Russia's announcement of a partial mobilisation of army reserves is "the most significant development" in the war since the Russian invasion started in February.

Mr Coveney will take part in a special meeting of the UN Security Council in New York tomorrow to discuss the Ukranian situation and expects a "very robust and blunt" debate.

Ireland will host a meeting on UN peacekeeping missions and will make a significant donation to a fund to combat diseases in the developing world.

This country currently deploys more than 500 Defence Forces and garda personnel on UN peace missions.

Joe Biden addresses the United Nations General Assembly at its headquarters in New York

Among those attending the event is the UN Under-Secretary-General for Peacekeeping, Jean-Pierre Lacroix.

Ireland will also announce a €65 million contribution to the UN Global Fund for combatting AIDS, malaria and TB at a conference chaired by President Biden.

Over the last decade, Ireland has given €273 million to this fund.

It is the country's single most significant investment in global health programmes.

The Global Fund claims to have saved 50 million lives to date through programmes against TB, malaria and HIV/AIDS, and is seeking to save a further 20 million lives over the next three years.

During the past three years, Ireland has donated €50 million to the fund. The €65 million contribution over the next three years is a significant increase.

Mr Coveney will also attend another US-hosted pledging conference, this time to raise funds to combat malnutrition.

The US bilateral development aid programme USAID, which is led by Irish-born Samantha Power, has pledged $200 million to a fund to tackle malnutrition in children.

It is seeking a further $250m from other countries, and Ireland is expected to make a significant contribution to this fund.

Childhood malnutrition accounts for one in five deaths of children under the age of five.

With a growing threat of a global food shortage next year, the issue of childhood malnutrition is particularly acute.

828 million people in the world are estimated to suffer from hunger - an increase of 150 million since 2019.

The Covid pandemic and the ongoing droughts in several parts of the world have contributed to a worsening of global poverty indicators, after years of progress in reducing the number of people affected by poverty.

The UN has been urging member states to step up support for anti-poverty programmes to get back on track with the millennium development goals.

Much of the day’s events will revolve around the president of the host country, Joe Biden.

Taoiseach Micheál Martin will arrive in New York tonight, and will attend a reception for heads of state and government, hosted by President Biden.