A successful round of ministerial talks to deepen free world trade is possible in Mexico later this year despite missed deadlines in completing objectives set in 2001 at Doha, the director general of the World Trade Organisation said on Wednesday.

"We need to make amends and compensate for the missing of deadlines last year," Supachai Panitchpakdi told an international business conference in Hyderabad. "I must continue to be optimistic. I see winds of optimism."

Ministers from the 145-nation Geneva-based organisation are due to meet at Cancun in Mexico in September this year against the backdrop of an unfinished agenda set in an agreement reached at Doha in Qatar in 2001.

Differences have cropped up on several issues, among which are the provisions of medicines for the poor across the world and issue of agricultural tariffs.

In the case of drugs for life-threatening diseases, developing countries have come up with a wide range of diseases, medicines for which should be exempt from patent laws through compulsory licensing provisions.

Such licensing can enable the sale of copycat generic medicines, which threaten sales by firms in advanced countries like the United States.

The US has agreed on some diseases, but a debate rages on a wide range of diseases linked to public health. A deadline had been set to address the issue by December-end, but a conclusion has not been reached.

Developing nations like India are also concerned that the US moved ahead with a farm bill that promotes agricultural subsidies, which they say goes against its own commitment to lower tariffs.

Supachai said the WTO expected to iron out differences on patents and also the question of having differential industrial tariffs to help developing nations by February. Issues related to free trade in services and agriculture were expected to be addressed a month later.