(Reuters) - Companies and law enforcement agencies nervous about a huge expansion in Internet domains - adding to .com, .net and others - will have many ways to protect trademarks and identify website owners, the head of the organization that organizes the Internet said on Tuesday.

The Internet Corporation for Assigned Names and Numbers begins accepting applications on Thursday for a hugely expanded number of Web domains. Verisign, which runs the .com registry, has estimated there will be up to 1,500 applications, which cost $185,000.

Many corporations view the proliferation of top level domains as a giant problem. Companies already hire lawyers to defend their trademarks online and most were forced to spend money recently to ensure trademarks were not on the sexually oriented .xxx domain when it was introduced.

Following complaints from the Federal Trade Commission and others that registries of website owners were sometimes poorly maintained, making it difficult to shut down scams, ICANN CEO Rod Beckstrom pledged that the top executives of all new registrars would undergo criminal background checks.

But Beckstrom argued that privacy groups and others pushed back against calls for detailed registries of website owners, called the WHOIS database.

WHOIS is a really tough problem, he said.

Warren Adelman, CEO of Go Daddy which sells website names, said he had supported the go-slow approach urged by law enforcement and some members of Congress.

We strongly recommended that there be a small pilot program and then expand that as sort of a measured way, he said.

In general, those who work with ICANN closely say privately the organization does a fairly good job of the very tough task of organizing the Internet internationally. The main criticism is that it sometimes fails to explain the reasoning behind its decisions, making it look high-handed.

In response to companies' concerns about trademarks, Beckstrom said that, in early May, ICANN would publish who had applied for what top level domain and allow protests.

Trademark violators would be shut down quickly, he said in a presentation at the Center for Strategic and International Studies think tank.

Sixty-one domain registrars have been stripped of their registrations or not renewed since 2003 because of violations such as failing to maintain proper documentation of who ran websites, failure to pay fees, or other problems, says Stacy Burnette, director for contractual compliance at ICANN.

TO MARKET, TO MARKET

Beckstrom argued the expansion gave new opportunities for companies.

Not everybody has the domain name they want today, he said.

He also argued the expansion would create a more international Internet by allowing top level domains in Chinese, Hindi and other languages that do not use the Latin alphabet.

Just in English, there could well be hundreds of applications for city names such as .Berlin or .Paris and many others for generic words such as .music or .food.

Theo Hnarakis, CEO of Melbourne IT Group which counts 3,500 companies among its clients, said about 100 of his clients were registering top level domains, some to prevent cybersquatting and others as a branding opportunity.

We are seeing some companies with a sense that this is a wonderful marketing opportunity, he said. Overstock applied for O.CO (following the last round of expansions). Why? Because ... the shorter the name, the more memorable it is.

If customers do not use search engines to find businesses but URLs instead, companies could save millions on paid click advertising, Hnarakis added.