(Rewrites; adds CEO quotes in 4-5 and 10, details in paragraphs 6-9 and analyst quote in paragraphs 11-12)

PARIS, Feb 15 (Reuters) - Pernod Ricard's shares rose 6% on Thursday, even after the French spirits maker cut its full-year sales forecast and share buyback programme as hoped-for improvements in the United States and China failed to materialise.

The world's second-largest spirits maker said it now expects full-year sales to flatline, after previously forecasting growth.

It also expects to buy back 300 million euros ($322 million) worth of shares for the year, down from the 500-800 million anticipated previously.

But the maker of Martell cognac, Mumm champagne and Asbolut Vodka said it was confident the second half of its fiscal year would be better.

"Four months ahead of the end of the financial year we have a little bit more visibility on how we can end," CEO Alexandre Ricard said.

Pernod had been banking on signs of improvement in two of its biggest markets: the United States and China.

But instead, in the second quarter retailers in the United States continued to cut expensive spirits from their inventories after high interest rates drove up the cost of holding them.

In China, a tough economy weighed on consumer demand ahead of the key Lunar New Year, a celebration that is normally a boon for spirits.

Pernod saw steep declines in first-half net sales in the United States and China, which fell by 7% and 9% respectively, with all but two of its key strategic international brands also in negative territory globally.

Ricard said that U.S. inventories were so tight in some cases that it could lead to spirits going out of stock. In China, however, the company is yet to see any impact on trading from an anti-dumping probe into EU brandies like cognac, he continued.

Edward Mundy, analyst at Jefferies, said there was a growing conviction that Pernod was reaching the trough of its performance, adding the shares were inexpensive given Pernod's medium-term potential.

Pernod also maintained its medium-term guidance of 4% to 7% top line growth, which some had feared might be cut.

Overall, half-year sales were down 3% organically, matching analysts' expectations.

($1 = 0.9314 euros) (Reporting by Dominique Vidalon in Paris and Emma Rumney in London Editing by Kim Coghill and Mark Potter)