LISBON, Sept 27 (Reuters) - Venezuela’s leftist President Hugo Chavez said on Saturday it was the capitalist system that had caused the financial crisis in the United States and the country should come up with a new constitution.

Speaking to reporters in Lisbon on the last leg of a tour that included visits to China and Russia, he said: “I think the United States should start a constituent process to create a constituent assembly, a new truly democratic model.”

A constituent assembly is a body elected to draft and sometimes adopt a new constitution.

“It was capitalism that caused the ruin” in the United States, said Chavez, who is one of Washington’s fiercest critics, calling the financial crunch “the worst financial crisis in history”.

“Let the U.S. empire end and let a great nation and great republic rise from the ruin ... It’s time to shout ‘Liberty!’ again in the United States,” Chavez said, calling for a new government to be free of the “dictatorship of the elite” such as big banks and corporations.

Critics accuse Chavez of running an authoritarian, Cuban-style regime in oil-rich Venezuela.

Chavez, who has signed various deals from weapons to energy this week in China and Russia also signed an agreement with Portugal’s Socialist government on Saturday to buy 1 million ultra-cheap laptops for schools and 50,000 pre-fabricated houses in deals worth $3 billion.

They also signed a draft deal between Energias do Portugal EDP.LS and Venezuelan state oil company PDVSA for the development of a liquefied natural gas project from the Blanquilla Este reserve in northern Venezuela.

The computers, which the government started distributing in Portuguese primary schools this week at a subsidised price of 50 euros ($73.15), will be delivered to Venezuela from December. They cost 285 euros in stores in Portugal.

The laptop is based on Intel Corp's INTC.O Classmate PC, a cheap computer that has been adopted in various formats in countries such as Brazil and Indonesia. (Reporting by Shrikesh Laxmidas; Writing by Andrei Khalip)