WASHINGTON (Reuters) - The G20 group of major economic powers will issue a statement next week encouraging countries that serve as "tax havens" to increase transparency and adopt international standards, a US official said on Saturday.

Michael Froman, deputy national security adviser for international economic affairs, told reporters in a conference call the G20 nations had agreed on the need for reform in that arena.

"I think there is broad agreement among the G20 that it's important to bring the offshore financial centres into the overall community of the global economy and under appropriate rules of the road," he said.

"Ultimately it will be represented in the leaders' communique, of things that can be done to encourage them to adopt international standards of behaviour around transparency and disclosure and things of that sort."

Mr. Froman noted there were no such offshore financial centers among the G20 countries, but he said talks with such centres were ongoing.

"There are a series of dialogues going on in various international fora, as well as between G20 members and some of the offshore financial centers," he said.

"But this will be reflected ultimately in the leaders' statement that would come out of London in terms of how best to encourage them to adopt these international standards of behaviour."

Earlier this month, Switzerland, Austria and Luxembourg offered to relax strict bank secrecy in some tax evasion cases in a response to a global crackdown on tax havens.

They were all on a list of countries given to the G20 by the Organisation for Economic Cooperation and Development (OECD), which polices countries it considers tax havens.

An OECD blacklist of unco-operative tax havens currently includes only Liechtenstein, Andorra and Monaco, but France and Germany have been pushing for others, including Switzerland, to be added.

German Finance Minister Peer Steinbrueck said this month he did not think G20 leaders would come up with a blacklist of tax havens at their upcoming summit.

Earlier this month, Senator Carl Levin introduced a beefed-up version the Stop Tax Haven Abuse Act, a bill which he originally co-sponsored with Barack Obama last year before he became President, with Bermuda on the list of "secretive jurisdictions" targeted by the Act.

Meanwhile, the Island is also expected to be on British Prime Minister Gordon Brown's blacklist of harmful tax havens set to be unveiled before the London G20 meeting next month, according to UK Sunday newspaper, The Observer.

The paper said the list is expected to include offshore centres linked to Britain, including Bermuda and the Cayman Islands.