WASHINGTON (REUTERS) - United States (US) Secretary of State John Kerry will donate five percent of his annual salary to charity, joining President Barack Obama and other officials in a show of solidarity with government workers forced to take unpaid leave as a result of deep spending cuts.

Kerry would contribute US$9,175 (S$11,400) from his US$183,500 State Department salary "to an appropriate charity that will benefit employees of the State Department", department spokesman Victoria Nuland told reporters on Thursday.

The funds would likely go to charities that support US diplomats who have been injured or killed in the line of duty, or that support children of employees, she said.

"We're still looking at the best choice and whether all of the money will go to one, or whether it'll be spread" between different charities, Ms Nuland said.

Defence and non-defence discretionary spending has shrunk across the board as a result of reductions under a process known as sequestration. To maintain critical functions, many agencies are making workers take unpaid leave, or furloughs.

Mr Obama's self-imposed 5 per cent pay cut from his US$400,000 salary would be effective from March 1, when the spending cuts began, and would last through the end of December, an administration official said on Wednesday.

Defence Secretary Chuck Hagel will give back the equivalent of 14 days of pay to the government, about US$10,750, his spokesman said on Tuesday.

Before taking up his post as the top US diplomat early this year, Mr Kerry was ranked as the richest member of the US Senate, with a net worth estimated in filings for 2011 at between US$184 million and US$288 million.

Mr Kerry, 69, inherited money from his mother's family and is married to the widow of a wealthy heir to the H.J. Heinz Company.