LONDON (AP) ¿ The British government has pledged $100 million to expand the Tate Modern, the seven-year-old institution that claims to be the world's most popular gallery of modern art.

Designed for 1.8 million visitors a year, the Tate Modern currently draws five million a year. The project, expected to cost $445 million by completion in 2012, will add 60 percent more floor exhibition space to the former power generation plant and is envisioned as the heart of development on the south side of the Thames, opposite St. Paul's Cathedral.

"Today's announcement is an important endorsement by government of the contribution that the arts make to society as a whole and the importance of British art at an international level," said Tate director Nicholas Serota.

"It gives us a platform for the creation of an institution for the 21st century, designed to serve the next generation of artists and visitors."

The Tate Modern, which doesn't charge admission, draws twice as many visitors a year as the Museum of Modern Art in New York or the Pompidou Center in Paris.