* Obama wants "new beginning" with communist Cuba
* U.S. leader seeks "equal partnership" in Americas
* Obama shakes hands with Venezuelan President Chavez
* "I want to be your friend," Chavez tells Obama (Adds Chavez, Obama comments on handshake, paragraphs 14, 16; other details, paragraph 17)
By Jeff Mason and David Alexander
PORT OF SPAIN, April 17 (Reuters) - U.S. President Barack Obama pledged on Friday to seek a "new beginning" in ties with communist-ruled Cuba as part of a new era of U.S. partnership and engagement with Latin America and the Caribbean.
Before addressing his counterparts in the hemisphere at the Fifth Summit of the Americas in Trinidad, Obama also initiated a handshake with Venezuelan President Hugo Chavez, one of Washington's most virulent critics in the region.
"We cannot let ourselves be prisoners of past disagreements," Obama told the opening session of the summit after entering the conference center to warm applause.
Obama promised U.S. cooperation to help the region fight the effects of the global economic crisis and confront the challenges of climate change and insecurity posed by drug-trafficking and kidnapping.
But he made a point of referring to Cuba, whose government has been at ideological odds with Washington for half a century following Fidel Castro's 1959 revolution.
"The United States seeks a new beginning with Cuba. I know there is a longer journey that must be traveled in overcoming decades of mistrust, but there are critical steps we can take toward a new day," Obama said in his address.
"Over the past two years, I have indicated -- and I repeat today -- that I am prepared to have my administration engage with the Cuban government on a wide range of issues -- from human rights, free speech and democratic reform to drugs, migration and economic issues," he added.
His speech before 33 other leaders from the hemisphere came a day after Cuban President Raul Castro had said his government was ready to talk about "everything" with the United States, including political prisoners and press freedom.
Earlier this week, Obama relaxed parts of the 47-year-old U.S. trade embargo against Cuba, and the conciliatory signals from both sides have raised hopes across the hemisphere of a historic rapprochement between Washington and Havana.
Cuba is excluded from the Trinidad meeting of 34 leaders, and in the past has angrily rejected any attempt to link an improvement in ties with Washington with internal reform.
Regional heads of state, from Brazil's Luiz Inacio Lula da Silva to Venezuela's Hugo Chavez, have called on Obama to end the long-standing U.S. embargo against Cuba.
'AN INTELLIGENT MAN'
Obama's handshake with Chavez also heralded a possible improvement in ties with one of the most important oil suppliers to the United States. Under conservative President George W. Bush, Chavez emerged as a voluble leader of pro-Cuba left-wing presidents and critics of Washington's policies.
"I want to be your friend," a beaming Chavez told the U.S. president, and photographs of the encounter were quickly distributed by the Venezuelan presidency.
"We shook hands like gentlemen; it was obvious it was going to happen," Chavez told reporters later. "President Obama is an intelligent man, different from the previous one."
A senior U.S. official said Obama went over to Chavez to introduce himself and they shook hands.
Asked later by reporters what he had said to Chavez, Obama replied: "I said, 'Como estas?'" -- Spanish for "How are you?"
Before he spoke at the opening session, Obama heard other speakers at the session, including Argentine President Cristina Fernandez and Nicaraguan President Daniel Ortega, call forcefully for an end to the U.S. embargo on Cuba.
In his rambling speech to the opening session, former guerrilla leader Ortega said he was "ashamed" to be attending a summit at which Cuba was not present.
In response, Obama, who earlier also shook hands with Ortega, departed from his prepared remarks to say: "I think it is important to recognize, given the historic suspicions, that the United States policy should not be interference in other countries."
"But that also means that we can't blame the United States for every problem that arises in the hemisphere ... That is the old way, we need a new way," he added.
In his address, Obama also promised to work with countries in the hemisphere to help the region confront the recession, stimulate economic growth and create jobs.
He also announced a new initiative to invest $30 million to strengthen cooperation on security in the Caribbean.
Before Obama landed in Port of Spain, White House spokesman Robert Gibbs called on Cuba to free political prisoners.
Hours before the start of the Americas summit, Venezuela's Chavez and a group of like-minded leftist leaders, including Cuba's Raul Castro and Ortega, rejected the proposed draft declaration of the meeting.
They said the meeting offered no solutions to the economic crisis and "unjustifiably excluded Cuba." (Additional reporting by Patrick Markey and Guido Nejamkis in Port of Spain; Writing by Pascal Fletcher; Editing by Will Dunham)