US Secretary of State Hillary Clinton and her Russian counterpart are to discuss the Syrian crisis in Dublin.
Mrs Clinton, Russian foreign minister Sergey Lavrov and United Nations envoy for Syria Lakhdar Brahimi will meet while in the capital for the Organisation for Security and Co-operation in Europe (OSCE).
There is a major security operation around the city for the two-day conference, which is being attended by some of the biggest political names in the world.
Mr Gilmore, chairperson-in-office of the OSCE, said: "I am very glad that this meeting here in Dublin has been able to facilitate this very important meeting between the secretary of state of the United States, the foreign minister of Russia and and the UN special envoy on Syria because as we all know what has been happening in Syria for quite some time is absolutely unacceptable - the slaughter of people, the humanitarian situation.
"I'm very pleased that this meeting in Dublin has become the venue for what is a real key meeting in the Syrian crisis."
Russia, one of Syria's closest allies, is believed to be key to quelling a 17-month-old uprising against President Bashar al-Assad in which 20,000 people have been killed.
Earlier, Mrs Clinton thanked Ireland for hosting the conference and for its year-long chair. "We applaud your work as chair and office of the OSCE to reaffirm this organisation's core principals and strengthen its capacities to promote peace and security, champion democracy and defend universal human rights and dignity," she said.
During her two-day visit to Ireland, Mrs Clinton will also deliver a speech on global human rights at a Dublin university, meet President Michael D Higgins and hold talks with Mr Gilmore and Taoiseach Enda Kenny. She travels to Northern Ireland on Friday.
The OSCE Ministerial Council is the largest international meeting organised in Ireland and is the culmination of the country's year-long chairmanship of the body. More than 50 foreign ministers, including Britain's Foreign Secretary William Hague, and 1,500 delegates from over 70 countries and international organisations are taking part.