UPDATE 4-TransCanada profit down, Keystone nears completion

* Net income falls 26 pct to C$334 million

* Comparable earnings of C$0.55/shr match estimate

* First phase of Keystone nears completion

* Shares up 1.6 pct (Updates shares. In U.S. dollars unless noted)

By Scott Haggett

CALGARY, Alberta, May 1 (Reuters) - First-quarter profit at TransCanada Corp (TRP.TO) sagged 26 percent from a year earlier quarter that was burnished by a big one-time gain, the country's biggest power and pipeline firm said on Friday.

TransCanada, which has expanded its gas pipeline network across much of North America and built up its power generation business, earned C$334 million ($280 million), or 54 Canadian cents a share, down from C$449 million, or 83 Canadian cents, in the first quarter of 2008.

The company is just a months away from completing the first phase of its $12 billion Keystone pipeline, which will eventually carry 1.1 million barrels of oil sands crude a day from Alberta to refineries in the U.S. Midwest and Gulf Coast.

Hal Kvisle, TransCanada's chief executive, told reporters that oil shipments to refineries in the Wood River, Illinois, region could begin early next year or sooner, as it completes the first, $5.2 billion, phase of the Keystone line.