Taoiseach Brian Cowen extended his congratulations to US president Barack Obama on winning the Nobel Peace Prize.
The US leader was commended for his extraordinary efforts to strengthen international diplomacy and co-operation between peoples.
The Taoiseach said the committee rightly recognised the President’s endeavours in diplomacy.
“In his first year of office, President Obama and his administration have sought to address many difficult international challenges and issues,” said Mr Cowen.
“He has worked patiently with countries from the Middle East and elsewhere, at the United Nations, the G20 and with the European Union partners to overcome them.”
The Norwegian Nobel Committee said only very rarely has a person captured the world’s attention and given its people hope for a better future to the same extent as Mr Obama.
The committee also attached special importance to Mr Obama’s vision of and work for a world without nuclear weapons.
The Taoiseach said the continued engagement of President Obama and the US to secure peace and prosperity in Northern Ireland was deeply appreciated by the Government and the people of Ireland too.
“Ireland has consistently supported the need for sustained diplomatic engagement on disarmament and I welcome the US President’s efforts in this regard,” added Mr Cowen.
Norwegian Prime Minister Jens Stoltenberg made clear the award carried big expectations, saying: "This is a surprising, an exciting prize. It remains to be seen if he will succeed with reconciliation, peace and nuclear disarmament."
Afghanistan's Taliban mocked the choice, saying it was absurd to give it to Mr Obama when he had ordered 21,000 extra troops to Afghanistan this year.
"The Nobel prize for peace? Obama should have won the 'Nobel Prize for escalating violence and killing civilians'," Taliban spokesman Zabihullah Mujahid said.
Japanese president Yukio Hatoyama and German Chancellor Angela Merkel both said the prize should encourage everyone to help Mr Obama rid the world of nuclear weapons.
"I think the peace prize was given with such a hope," Mr Hatoyama told reporters on a visit to Beijing.
Ms Merkel said Mr Obama had shifted the tone towards dialogue in a very short time. "There is still much left to do, but a window of possibility has been opened," she said in Leipzig.
UN secretary general Ban Ki-moon praised Mr Obama's multilateralism. "His commitment to work through the United Nations gives the world's people fresh hope and fresh prospects," he told reporters.
In the Middle East, chief Palestinian peace negotiator Saeb Erekat said the award could be a good omen for the region.
"We hope that he will be able to achieve peace in the Middle East and achieve Israeli withdrawal to 1967 borders and establish an independent Palestinian state on 1967 borders, with Jerusalem as its capital," he said.
Israeli prime minister Benjamin Netanyahu said Mr Obama had inspired many people. "I look forward to working closely with you in the years ahead to advance peace and to give hope to the peoples of our region who deserve to live in peace, security and dignity," he wrote in an open letter congratulating Mr Obama.
The Islamist movement Hamas, which controls the Gaza Strip and opposes a peace treaty with Israel, said: "Unless real and deep-rooted change is made in American policy towards recognising the rights of the Palestinian people I would think such a prize would be useless," Ismail Haniyeh, Hamas prime minister in the Gaza Strip, told reporters after Friday prayers.
In Iraq, the government welcomed the award, saying Mr Obama deserved it because he had led a dialogue with other nations.
Additional reporting: Reuters