Ames started the day six shots behind Jamie Spence and four behind David Gilford, but he caught the Englishmen with a brilliant round, covering the last six holes in five under par.
All three players are on 208, eight under par, with their nearest challengers, the South African Wayne Westner and Vicente Fernandez, of Argentina, six shots further back.
Ames, who qualified for the European Tour only last November, comes from Trinidad and Tobago has admitted giving a false nationality last year when trying to cross from Canada into the United States. He said he was an American because he was in a hurry.
'They found out where I came from and took away my visa,' Ames said. 'I'd been playing on the Ben Hogan Tour in the States for two years and could no longer play there. So I came to Europe and it has proved a real good move.'
Having played the first six holes in par, Ames had five birdies, plus an eagle at the 511-yard 17th where he holed out with a short pitch over a greenside bunker. He could have taken the lead, but missed a one-foot putt at the 12th. 'It was a mental mistake, I just rushed it,' he said.
Seve Ballesteros shot a third round 74 for 224, 16 shots off the pace, and then revealed that he had almost scratched from the tournament because of back trouble.
MOROCCAN OPEN (Golf Royal de Agadir) Leading third-round scores (GB and Irl unless stated): 208 J Spence 67 69 72; D Gilford 68 70 70; S Ames (Trin) 70 72 66. 214 V Fernandez (Arg) 77 67 70; W Westner (SA) 70 71 73. 215 R Karlsson (Swe) 75 67 73. 216 M Sunesson (Swe) 75 72 69; F Nobilo (NZ) 73 74 69; P Mayo 71 74 71; C Mason 76 69 71. 217 J Parnevik (Swe) 76 72 69. 218 M-A Martin (Sp) 70 75 73. 219 J Van De Velde (Fr) 75 76 68; M James 74 76 69; P Walton 77 72 70; A Lebouc (Fr) 72 77 70; A Hunter 75 73 71; D Smyth 75 73 71; R McFarlane 74 71 74; M McLean 74 72 73; D Clarke 76 67 76.
As the 1992 Amateur champion, Stephen Dundas of Scotland was yesterday invited to take part in this year's US Masters. He will be one of six newcomers at Augusta - Anders Forsbrand of Sweden, Tony Johnstone of Zimbabwe, Brett Ogle of Australia, Warren Schutte of South Africa and the Canadian Richard Zokol are the others. Four more Britons received invitations - Nick Faldo, Ian Woosnam, Sandy Lyle and Colin Montgomerie. The tournament will take place between 8 and 11 April.Reuse content