Clarke was three under par for the last 11 holes on Friday

The pair, who share an agent, both birdied the last to reach two under for 36 holes, four behind Chad Campbell.

Clarke, 37, was one over after a bogey at the 7th but then picked up three shots over the next 11 holes for a 70.

The 30-year-old Howell added his second straight 71 thanks to three birdies and two bogeys, but compatriot Luke Donald is four further back after a 72.

As well as his birdies, Clarke also saved par superbly at the 13th after finding the creek with his approach.

Clarke, still without a major title, has a best of eighth in eight previous trips to the Masters.

There are a lot of people who want to win this a lot more than I do Darren Clarke Quotes of the day

The Ulsterman, whose wife Heather has been battling the return of cancer for the past 18 months, birdied the 465-yard last despite his drive finishing in a divot.

"I am very comfortable and relaxed out there and just taking whatever the course gives me," said Clarke, who led by three after an opening 66 three years ago but then fell away.

"I've forgotten what I should be doing and just gone out and hit it. It's working. It's probably the most relaxed I've ever been in a major."

He was in the Bahamas with his wife last week and added: "Sometimes when you get completely away from the game and hardly touch the clubs it brings back what is really important. And golf ain't that important.

"I'm not bothered about anything. If I make a mistake I make a mistake - and I made a few today.