UPDATE 1-Iran sanctions having impact-US Treasury official

(Updates with background, quotes, paragraphs 5 to end)

WASHINGTON, April 17 (Reuters) - U.S. financial sanctions against Iran are "having an impact" on international efforts to thwart Tehran's efforts to obtain nuclear weapons and aid terrorism, a senior U.S. Treasury official said on Thursday.

Daniel Glaser, the Treasury's deputy assistant secretary for terrorist financing and financial crimes, told U.S. lawmakers that many international banks are voluntarily going beyond their legal requirements under U.S. and U.N. sanctions to completely avoid doing business with Iran.

"Financial measures are an integral component of U.S. and international efforts to counter Iran's threatening behavior," Glaser said in prepared remarks to the U.S. House of Representatives Foreign Affairs Committee.

"Through our authorities and our engagement with counterparts around the world, we are implementing a financial strategy that is having an impact," he added.

The U.S. sanctions are aimed at cutting off sources of financing to Iran's nuclear program, which it says is aimed at developing nuclear bombs. Washington also accuses Iran of providing financial support to international terrorist groups.

Glaser said the United States also has recently warned banks that Iranian banks, including several that have been specifically blacklisted by the U.S. Treasury, have been requesting anonymity in international transactions to try to avoid U.S. sanctions. Iran's central bank, Bank Markazi, also has been using the same elusive practices, he said.

Through coordination with the multinational Financial Action Task Force, Glaser said several countries have warned their financial institutions of the risks inherent in doing business with Iran, including the UK, Canada, France, Germany, Japan and Malaysia. (Reporting by David Lawder; Editing by Neil Stempleman)