Cuban President Raul Castro has warned that the island's revolution is at stake if his proposed economic reforms are not adopted.
The government is about to undergo the first major overhaul of Cuba's state-run system since the 1960s.
It wants to expand the private sector and reduce the role of the state.
Mr Castro's two-hour speech to the closing session of parliament was his longest since taking over the presidency from his brother, Fidel.
"We are playing with the life of the revolution," he told legislators.
"We can either rectify the situation, or we will run out of time walking on the edge of the abyss, and we will sink."
This Caribbean island's unproductive Soviet-style command economy is in deep financial trouble, and the government can no longer afford the massive subsidies that make up for low wages.
Half a million state workers are due to lose their jobs, while restrictions are being eased on people who want to become self-employed or set up small businesses.
President Castro said the changes would not turn Cuba capitalist.
The aim, he said, was to strengthen the socialist system created by his brother Fidel Castro after the revolution in 1959.
The president also used the speech to attack the Obama administration's policies towards Cuba.
"There isn't the slightest willingness on the part of the United States to change its policy, which is irrational and doesn't have an ounce of credibility," he said.
With new presidents installed in both countries two years ago, expectations were raised that these Cold War enemies might finally settle their differences.
There have been some small but symbolic changes on both sides.
But the decades-old US trade embargo remains firmly in place, as does the ban on most Americans tourists visiting the island.