By Nina Chestney and Agnieszka Flak

LONDON (Reuters) - A U.N. committee has completed the draft design of a fund to help developing countries tackle climate change, paving the way for its launch in 2013, the U.N.'s climate chief said on Friday.

Last year, countries agreed to create the 'Green Climate Fund' to channel up to $100 billion a year by 2020 to developing countries to help fight climate change.

An international committee in charge of designing the fund met this week in South Africa, but some organizations accused the United States and Saudi Arabia of hampering the process.

Negotiators from around the world will consider whether to approve the design at next month's U.N. climate summit in Durban, where hopes have faded for sealing a new globally binding climate pact to succeed the Kyoto Protocol from 2013.

"The Committee ended its work by submitting for consideration and approval in Durban both a draft instrument for the Green Climate Fund and recommendations on transitional arrangements to get it launched quickly," Christiana Figueres, executive secretary of the U.N. Framework Convention on Climate Change, said in a statement emailed to Reuters.

"The submissions (...) include a strong signal to engage the private sector and a solid basis to develop country-driven operations through direct access to funds."

"Once approved in Durban, they would allow the fund to grow quite quickly, especially as the financial environment improves, and the way would be open for a fairly rapid set-up of the fund in 2012 and full initial operations in 2013," she added.

The UK-based International Institute for Environment and Development (IIED) said on Thursday that the United States and Saudi Arabia had withdrawn their support for the overall design of the fund due to concerns about some wording of the text.

At a U.N. meeting in Panama last month, more than 100 of the world's poorest nations accused the United States of blocking talks on how to scale up climate finance.

Some of the poorest nations in Africa and Asia -- which are particularly vulnerable to climate change -- have been urging more direct access to the fund and want to make sure green finance is in place before committing to a binding climate pact.

They argue that national climate change trust funds in developing nations should be able to access the Green Climate Fund directly, rather than going through a third party such as the World Bank, which entails long delays and excessive paperwork, the IIED said in a statement.

"Direct access would allow more devolved decision-making to reflect local and national concerns and it would enable countries to integrate the funding into their national plans and strategies for dealing with climate change," said Pa Ousman Jarju, chair of the Least Developed Countries negotiating block at the U.N. climate change talks.

(Editing by Jason Neely)