* TSX down 21.05 points at 13,011.62
* Five of 10 main sectors lower
* U.S. macro concerns overshadow earnings (Updates with details, comments)
By Andrea Hopkins
TORONTO, July 28 (Reuters) - Toronto's main stock index was slightly lower on Thursday morning after a see-saw open, as uncertainty over the U.S. debt ceiling talks made investors reluctant to commit, despite a slew of earnings news.
Heavily weighted energy and materials led five of the TSX's 10 main sectors lower. Materials dropped 1.1 percent while energy issues fell 0.7 percent as U.S. crude turned lower after a brief rise on U.S. jobless claims data. [O/R]
Traders said investors remained edgy about the U.S. debt ceiling talks and markets are expected to be volatile ahead of a vote later in the day on a bill to cut the U.S. deficit.
"There are a lot of earnings but the macro headwinds of the debt ceiling still loom large, so the market is reluctant to move solidly in one direction or the other," said Paul Taylor, chief investment officer at BMO Harris Investment Management Inc.
At 10.27 a.m. (1427 GMT), the Toronto Stock Exchange's S&P/TSX composite index .GSPTSE was down 21.05 points, or 0.16 percent, at 13,011.62.
Taylor said the market is watching the wave of earning reports but is unlikely to make big bets heading into the final weekend before an agreement needs to be reached by U.S. lawmakers over the debt ceiling.
"Only if earnings are significantly above or below consensus will we get a big move. The market is more focused on the macro events of the weekend and getting set for that," Taylor said.
Gold and energy companies led the decliners amid a slew of earnings reports.
Goldcorp Inc (G.TO) was the most heavily weighted decliner on the index, down 5.3 percent to C$45.68. The gold producer said on Wednesday its second-quarter operating profit more than doubled but the company cut the mid-point of its expected 2011 gold production range by 6.5 percent, as operational issues, project delays and forest fires curtailed output in Mexico, Canada and the Dominican Republic. [ID:nN1E76Q1O3]
Barrick Gold Corp (ABX.TO) was also down, falling 2.2 percent to C$44.98, even though the world's largest gold miner reported a 35 percent increase in its second-quarter profit. [ID:nN1E76R019]
Talisman Energy Inc TLM.TO fell 5.4 percent to C$17.74. Canada's third-largest oil explorer said second-quarter earnings rose 22 percent, helped by higher oil prices, but the company expects delays in projects and production ramp-ups to squeeze output for the year.
Suncor Energy (SU.TO) fell 1.5 percent to C$37.55 after the oil and gas producer posted a slim 4 percent rise in second-quarter profit and said it did not anticipate entering into further agreements to sell assets in 2011. [ID:nL6E7IS0CL]
Among the gainers, Potash Corp (POT.TO) shares climbed 2.8 percent to C$57.64 as the world's largest fertilizer maker reported a 75 percent increase in its quarterly profit on the back of surging grain prices that lifted demand for its crop nutrient products. [ID:nN1E76Q2DX]
Shares in Thomson Reuters Corp. (TRI.TO) were also higher, up 3.4 percent at C$33.03. The gain came despite reports by the company of sluggish growth in its Markets division. [ID:nN1E76Q1HG]
Offsetting some of the uncertainty was healthy economic data from the United States, which helped buoy markets south of the border. New claims for U.S. jobless benefits fell below 400,000 for the first time since early April, while pending sales for existing homes showed an unexpected rise. [.N]
($1=$0.95 Canadian) (Reporting by Andrea Hopkins; editing by Rob Wilson)