UNITED NATIONS (Reuters) - The United States on Tuesday launched a program to defend journalists around the world from legal threats aimed at silencing critical voices, a growing tactic that top U.S. aid official Samantha Power described as "lawfare."

Power, administrator of the U.S. Agency for International Development (USAID), announced the Reporters Shield program at an event to mark World Press Freedom Day at the United Nations.

"Many independent outlets can't afford to be sued, so they are driven out of business or they try to self censor to avoid attracting the interest of those who might target them," she said. "Corrupt leaders know all this, which is why they're using lawfare more and more."

USAID said it plans to work with Congress to provide up to $9 million for the Reporters Shield program that will be jointly managed by the Organized Crime and Corruption Reporting Project and the Cyrus R. Vance Center for International Justice.

"To withstand lawfare journalists and media outlets need robust protection, they need training in how to avoid lawsuits altogether, they need resources to hire lawyers and cover legal fees," Power said.

USAID said Reporters Shield will be a membership program and organizations will pay an annual fee based on factors like the outlet's location and how many stories they produce a year.

(Reporting by Michelle Nichols; Editing by David Gregorio)