NEW YORK (Reuters) - The Washington Post is closing its last US bureaus outside the nation's capital as the money-losing newspaper retrenches to focus on politics and local news.

"At a time of limited resources and increased competitive pressure, it's necessary to concentrate our journalistic firepower on our central mission of covering Washington and the news, trends and ideas that shape both the region and the country's politics, policies and government," the newspaper's top editor, Marcus Brauchli, wrote in a memo to employees that was obtained by Reuters.

The Post will close its bureaus in Chicago, Los Angeles and New York, effective December 31.

The news comes after the Post told several employees at its website that they would be laid off, and follows several rounds of buyouts in recent years.

The Post, like nearly every other US newspaper, has been battered by falling advertising revenue and circulation as readers get more news online for free.

With a circulation of more than 582,000 copies, the Post is the fifth most read daily newspaper on weekdays, according to figures released by the Audit Bureau of Circulations. It is the third most read Sunday paper, with paid circulation of more than 822,000 copies.

During the past four to five decades, it has made a franchise of covering national politics and government from the White House to Capitol Hill.

Unlike other big national papers including News Corp's Wall Street Journal, The New York Times and Gannett's USA Today, it limits most of its distribution to the Washington metropolitan area.

For a time, the Post and many US newspapers relied on big profits at their parent companies to send reporters on coveted assignments overseas and throughout the United States.

More recently, it has been trying to cut costs as ad sales shrink. It also is facing more competition from new news outlets, most notably Politico.com, run by two former Washington Post reporters, and staffed by plenty of other ex-Post workers.

Many US newspapers from The Boston Globe to Tribune Co's Baltimore Sun have closed bureaus around the country and around the world as they try to save money. Many experts say newspapers have a better chance of surviving if they stop trying to cover the world and report more local news.

"We are not a national news organisation of record serving a general audience. Nor are we a wire service or a cable channel," Brauchli told the Post's media columnist and reporter Howard Kurtz.

While none of the Post's six national reporters at those bureaus will be laid off, three news aides lost their jobs, the memo said.

Still, Brauchli wrote, the Post will cover the nation.

"We will continue to cover events around the country as we have for decades, by sending reporters into the field," he wrote.