American cycling champion Lance Armstrong is signing off for the year in Ireland.

Armstrong - who is racing in the three-day Tour of Ireland - has decided to make the Irish race his last official race for the year.

"It's a nice ending for him. He might do some mountain bike races or stuff but this is his last official race of the year," Astana team manager Johan Bruyneel said.

Armstrong finished the first section today and said he felt like he was breathing through a small straw.

"Done with st 1 of ToI," he posted on Twitter. "Up/down/left/right/windy!! I felt like I was breathing thru a straw. . A small straw."

Armstrong will stay on in Ireland after the race to speak at a three-day global cancer summit organized by his own Livestrong Foundation.

The Tour of Ireland, which started today in Dublin, covers 356 miles in three stages and ends in Cork on Sunday.

Armstrong arrived in Dublin yesterday after a whirlwind week which saw him take in a ride with 300 fans and a U2 concert in Glasgow on Tuesday and a charity circuit race in Oslo on Wednesday.

In fact, Armstrong flew down to London from Glasgow with Bono and the boys on U2's Air 360

Armstrong's last race in Ireland took place in 1992 which is the first year he turned pro.

Meanwhile, a one-minute silence was held at the start line today to remember top Irish amateur Paul Healion, who was killed on Sunday in a car crash.

Healion, 31, was due to compete in the event as part of the Irish national team.