Domain name oversight body the Internet Corporation for Assigned Names and Numbers (Icann) has admitted that its plans to launch new generic top-level domains (gTLDs) are running behind schedule, but insisted that they should still be available before the end of the year.

When brought into force, the new rules could allow the creation of any TLD with up to 64 characters, including regional suffixes, generic words and brand names.

However, the complexity of the issues involved, and Icann's desire to be as transparent as possible, means that the process is taking longer than initially thought, according to Icann's director of product services and communications, Karla Valente.

"Even though [gTLDs] will not launch on 30 September, as we said in our Cairo meeting, we are still working internally to launch in 2009," she said. " However, some overarching issues could delay things."

These issues include the cost of registration, the market impact of the new gTLDs, and the technical impact, for example whether there is enough space on the Domain Name System to accommodate them, Valente explained.

Icann has now commissioned third parties to study the technical and market impact of new gTLDs, and will hold various public meetings globally from April "in order to address these major issues through a series of discussions".

In addition, the second draft of the gTLD Applicant Guidebook was released today, containing explanatory memoranda and a detailed analysis of the first round of public comments on the proposals. The guidebook is likely to undergo another revision before the final version is released towards the end of the year, according to Valente.

The new rules for generic TLDs were broadly welcomed by .com registry VeriSign, although the firm agreed that various issues need careful consideration before they get the green light.

"The new TLDs will be very interesting. I strongly believe they will result in a great user experience and will encourage more growth and more competition, " said Tobias Wann, VeriSign's European leader of domain name services.

"But it has to happen in a thoughtful manner, taking into account the technical implications."