"I have committed US$73 million dollars in assistance to Zimbabwe," said Obama.
The aid "will not be going to the government directly because we continue to be concerned about consolidating democracy, human rights and rule of law, but it will be going directly to the people in Zimbabwe," he added.
Obama also praised the prime minister for trying to "lead Zimbabweans to more hopeful times".
He said that he has "extraordinary admiration" for the prime minister.
Obama said the U.S. wants to help "encourage the rule of law, human rights and basic health and education services in Zimbabwe".
President Robert Mugabe invited prime minister Tsvangirai into an inclusive Government in February.
Tsvangirai arrived in Washington this week as part of a three-week tour of Western countries, trying to persuade governments to offer some aid.
The U.S. administration has not responded positively to the prime minister’s call.
After a meeting between PM Tsvangirai and Secretary of State Hillary Rodham Clinton, State Department spokesman Ian Kelly said the administration would consider development aid if certain reform benchmarks are met.
PM Tsvangirai says that Zimbabwe urgently needs aid now. He warned in a speech Wednesday that overhauling the political and economic system in Zimbabwe could falter without aid.
"We are moving into a new phase, and that’s what needs to be rewarded rather than punished," he said in refernce to the inclusive Government.
On Thursday, a cartoon in a U.S. newspaper depicted PM Tsvangirai leaving the White House empty-handed, asking Obama what had happened to his slogan "Yes, we can."