HAVANA, April 30 (Reuters) - Former Cuban leader Fidel Castro on Thursday derided U.S. steps toward improving relations with the communist island, saying the United States wants Cuba to act like a slave willing to "accept again the whip and the yoke."

The 82-year-old Castro, writing in a column published on the Internet, said "the adversary should never be under the illusion that Cuba will surrender."

President Barack Obama has said he wants to recast U.S.-Cuban relations that have been hostile for 50 years, but insists on maintaining a U.S. trade embargo imposed against the island since 1962 to use as leverage for Cuban change.

He recently eliminated travel restrictions for Cuban Americans and called on Cuba to release political prisoners and improve human rights to get more concessions from Washington.

But Fidel Castro and his younger brother, President Raul Castro, view U.S. conditions as infringing on Cuban sovereignty, or worse.

"The collision between the great power of the North and the Cuban revolution was inevitable. The heroic resistance of the people of our small country was underestimated," Castro wrote.

"Today they are willing to forgive us if we will resign ourselves to returning to the fold as slaves that, after knowing freedom, will accept again the whip and the yoke."

Both Castros have expressed a willingness to talk with the United States, and informal, low-level talks have already begun in Washington.

But they publicly insist that Cuba does not have to make concessions to move the diplomatic process forward.