WASHINGTON, March 13, 2008 (AFP) - In an annual Saint Patrick's Day diplomatic ritual, US President George W. Bush will host Irish Prime Minister Bertie Ahern on March 17, the White House said Thursday.

'In keeping with a decades-old tradition, the two leaders will participate in the 'Shamrock Ceremony,' symbolizing the deep cultural roots and close ties of friendship between the United States and Ireland,' said spokesman Tony Fratto.

The two leaders will also hold talks and then meet with British Secretary of State for Northern Ireland Shaun Woodward and representatives of Northern Ireland's political leadership, civil society, and business community, he said.

Under political pressure, Ahern on Wednesday defended the departure of most of his government to 45 locations around the world as part of an annual St Patrick's Day migration.

The celebrations surrounding the national holiday on March 17 provides a 'framework to showcase modern Ireland all over the world,' Ahern told the Dail (lower house of parliament) on Wednesday.

'It is used by us as a marketing opportunity,' he said.

State broadcaster RTE, using details obtained under freedom of information laws, reported on Wednesday that last year's St Patrick's Day trips by officials and members of the government cost over 560,000 euros (861,000 dollars).