* CEO says July sales good, 'not pessimistic' on Q3
* North American, French sales growth slows
* H1 operating profit up 9.4 pct (Adds comments from conference call)
PARIS, Aug 31 French advertising agency Havas reported a slowdown in sales growth in the second quarter, with its home and North American markets putting the brakes on, but sounded a relatively upbeat note for the current quarter.
Chief Executive David Jones told analysts on a conference call that sales in July were good, adding that the company was "not pessimistic" about the third quarter for the moment.
He was speaking after Havas, which competes with larger rivals Publicis and WPP, posted second-quarter sales of 442 million euros ($557 million) and organic growth of 2.1 percent, compared with 3.5 percent in the first quarter.
First-half operating profit rose 9.4 percent to 93 million euros, giving it a margin of 11.2 percent.
Analysts had expected an operating profit of 100 million, according to a Reuters poll of six analysts.
Second-quarter organic sales growth slumped in France to 0.5 percent, although it improved in Europe overall to 1.9 percent from 1.1 percent in the first quarter.
North American growth slowed to 0.5 percent from 3.6 percent in the first quarter but Havas said the year-ago figure had been unusually strong.
Havas shares are up 26 percent so far this year, outperforming a 12 percent gain in the European media sector . ($1=0.7933 euros) (Reporting By Matthieu Protard and Gwenaelle Barzic; Editing by Greg Mahlich)