* Appetite still weak in key markets of Hong Kong, US
* Exports to China, Singapore fall after rise in August
* Swatch Group, Richemont shares drop on disappointing data
(Adds detail, shares, writes through)
ZURICH, Oct 22 (Reuters) - Demand for Swiss watches slipped 26 percent in September, reversing an easing in the pace of decline seen in the previous two months, as consumers in Hong Kong and the United States held back on spending on timepieces.
The value of sales dropped to 1.1 billion Swiss francs ($1.1 billion) in September, the Federation of the Swiss Watch Industry said on Thursday. Swiss watch exports have also fallen 26 percent so far this year, the industry body said.
"The base effect was again unfavourable for Swiss watch exports, with the trend failing to show any improvement in September," the federation said.
"The cumulative variation was unchanged in relation to August and indicated -25.9 percent for the first nine months of the year. This steady decline has reduced the value of watch exports to their 2006 level," the body said.
The industry, home to Swatch Group, the world's largest watchmaker, and luxury goods group Richemont, is facing its most severe drop in demand in 20 years as consumers cut back on spending on luxury items.
By 0736 GMT, shares in Swatch Group were trading 2.9 percent lower at 255.75 francs, while Richemont was some 1.6 percent weaker at 30.12 francs. The DJ Stoxx European personal and household goods index was 0.6 percent lower.
Shares in the two groups have rallied recently after a number of ratings upgrades.
"The data was disappointing and actually went backwards in countries such as China and Singapore that were positive in the previous month," said Kepler Capital Markets analyst Jon Cox.
Exports to Hong Kong, the industry's biggest market, slumped 30 percent, while demand in the United States fell 43 percent. China was down 1.1 percent and exports to Singapore fell 3.3 percent. (Reporting by Katie Reid; Editing by David Holmes) ($1=1.011 Swiss Franc)