WPP says clients still shy on spending

* April, May tougher for trading than Q1

* Clients more confident, but no increased spending yet

* May was not as good as April in China

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By Cyril Altmeyer

CANNES, France, June 25 (Reuters) - Clients are becoming more confident but this has yet to result in increased advertising spending, the chief executive of British advertising group WPP (WPP.L) said on Thursday.

April and May have been tougher for business than the first quarter, especially in Western Europe, Martin Sorrell, who heads the world's largest advertising group by revenue, told Reuters.

"Today CEOs are more confident. But that's in the head and in the heart. It has not extended to them writing checks," he said on the sidelines of the Cannes Lions 2009 ad festival.

WPP, whose advertising agencies include Ogilvy & Mather and Young & Rubicam, competes for budgets with the likes of France's Publicis (PUBP.PA) or Omnicom (OMC.N) of the United States.

Earlier this month, WPP said like-for-like revenue fell 6.7 percent in the first four months of the year, compared to a 5.8 percent fall in the first quarter.

Sorrell did not give indications for June on Thursday.

To counter the fall in revenue, WPP's headcount fell by almost 4,300 people or 3.7 percent in the four-month period, with over half leaving on a voluntary basis.

Headcount would "match what happens on revenue", Sorrell, said, when quizzed about the rest of the year.

A DIFFICULT YEAR

In April, Sorrell said WPP would not meet its full-year forecasts as firms cut marketing budgets amid a global downturn [nLS123215] and on Thursday did not discuss financial goals.