TOKYO — Japan’s government proposed a special $50 billion budget to help finance reconstruction efforts today and plans to build 100,000 temporary homes for survivors of last month’s devastating earthquake and tsunami.

The twin disasters destroyed roads, ports, farms and homes and crippled a nuclear power plant that forced tens of thousands of more people to evacuate their houses for at least several months. The government said the damage could cost $309 billion, making it the world’s most expensive natural disaster.

Prime Minister Naoto Kan said he was moved by his conversations with victims during a recent tour of shelters.

“I felt with renewed determination that we must do our best to get them back as soon as possible,” he told reporters.

The government approved an extra $50 billion to help finance the rebuilding, in what is expected to be only the first installment of reconstruction funding. About $15 billion will go to fixing roads and ports and more than $8.5 billion will go to build temporary homes and clear rubble.

“This is the first step toward rebuilding Japan after the major disasters,” Finance Minister Yoshihiko Noda said.

More than 27,000 people are dead or missing after the earthquake and tsunami hit northern Japan on March 11. About 135,000 survivors are living in 2,500 shelters set up in schools and community centers. Many others have moved into temporary housing or are staying with relatives.

Recovery efforts have been complicated by the crisis at the Fukushima Daiichi nuclear power plant, which lost its power and cooling systems in the earthquake and tsunami, triggering fires, explosions and radiation leaks in the world’s second-worst nuclear accident.

Plant operator Tokyo Electric Power Co., which said it will take six to nine months to bring the plant under full control, has been heavily criticized for its handling of the nuclear crisis.