MIAMI (AFP) - In an open letter to US President George W. Bush and his Democratic rival John Kerry, the leading Cuban-American lobby group called for tougher US policies against Cuba's communist government.

"In this election, Cuban-Americans are more concerned with substantial progress than ever before," the Cuban American National Foundation (CANF) said.

"Their interest is Cuba, and whoever provides a clear and credible vision to facilitate freedom will win their votes," the letter said.

Most of the 1.2 million Cuban-Americans live in Florida, a state that was decisive in determining the outcome of the 2000 presidential race and could again play a key role in the Bush-Kerry face-off in November. Cuban-Americans have traditionally voted Republican but a opinion polls indicate their support for Bush is dropping.

The CANF urged the US Justice Department to indict Cuban President Fidel Castro and his brother Raul over the 1996 death of four members of the Miami-based Brothers to the Rescue group killed when Cuban fighter jets shot down their aircraft.

It also called for direct assistance to dissidents within Cuba, and a continuation of the US embargo against the communist-run island.

The lobby group further urged authorities to scrap a policy under which Cubans caught at sea as they try to reach US shores are sent home.

"After interminably witnessing the abuses of the Castro regime, its devastation of the Cuban people, Cuba's support of terrorism, and Cuba's attacks upon the interests of the United States, you will find this electorate most impatient."

The letter was printed in the Miami Herald and the Spanish-language Nuevo Herald daily. It was addressed to Bush, with a footnote saying the same letter had been sent to Kerry.