Rory McIlroy's tied for the lead at the halfway stage of golf's BMW Championship and says he's "pretty pleased" to be below par into the weekend. 

At a high-scoring tournament, he'll begin day three on one-under-par following yesterday's 68.

"Yeah, it was really good," the Down man told reporters after his second-round in Chicago. "I got off to a nice start. A couple under through 4, 3-under through 10, sort of cruising, and then as it got later in the day, the golf course definitely became a little firmer, a little tougher.

"The wind got up a little bit. A little disappointed to drop those shots on the way in, but I think if you shoot anything under par on this golf course, you've got to be pretty pleased.

"I've driven the ball much better over the last couple of days, so that's been -- that's a huge key to my game.

"If I can drive the ball well, everything seems a bit easier from there. And I felt a bit better with the putter. I put my old putter back in the bag. I felt a little more comfortable over the sort of inside-10-feet range, so that felt better.

"But overall everything was pretty good. I think I finished like seventh or eighth in approach last week in Boston and obviously finished way down -- so my iron play and my wedge play has been pretty good the last few weeks, it's just about putting the ball in the fairway so I can take advantage of how well I'm hitting my irons and my wedges."

Patrick Cantlay shares the lead with McIlroy in Chicago with Hideki Matsuyama and Dustin Johnson heading up the chase at level-par.