By R. HART PHILLIPS

Special to The New York Times.

HAVANA, Nov. 1--The cuban rebel leader, Fidel Castro, has reached the height of his power in the rebellion against President Fulgencio Batista.  He constitutes the major and most pressing problem of the Government as it prepares to hold elections Monday.

This is admitted by close friends of the Government and none can deny that if Castro is not the master of the eastern end of the 750-mile-long inland he at least exerts supreme authority over large areas outside the cities, which are held by Government troops.  His followers are not alone in believing that he could take the cities were it not for the fact that he would thus provide the Batista forces with specific targets.

There is no doubt that Castro has developed extraordinary military power since he landed on the south coast of Oriente Province on Dec. 2, 1956, with an expedition of eighty-two men from Mexico.  At that time he was attacked by Government land, sea and air forces and his eighty-two men were reduced to twelve.  They fled into the jungle-covered Sierra Maestra, today his stronghold.

Many months later Castro had gathered several thousand men in the Sierra Maestra.  But they lacked arms and were faced with almost certain extermination by the forces of President Batista.

Then the dictatorship of Gen. Marcos Perez Jimenez fell in Venezuela.  Since that time revolutionary forces of Venezuela have reportedly been supplying Castro with arms and other aid.  Whatever his source, Castro has today a group of veteran guerilla fighters equipped with the best weapons.

Another decisive occurrence for Castro was the decision of the United States to stop supplying arms to the Batista Government.  The United States has recognized the Batista regime from the days in March, 1952, when it came to power by military coup against President Carlos Prio Socarras, now living in exile in Miami, Fla.  Nevertheless, the United States halted arms supplies to the Batista Government because they were being used against the people of the island.

Batista since has sought arms in other quarters.  Some have been obtained from Dominican Republic, which a small-arms factory, and form Nicaragua.  Great Britain has supplied jet planes and amphibious tanks.  In reprisal, Castro has threatened the British Ambassador and diplomatic officials.

The rebels have sworn to prevent elections at any cost.  Recently Castro's Twenty-sixth of July movement broadcast orders to all insurgents to shoot at any vehicle which moved on the highways and railway in Oriente Province from Oct. 30 through Nov. 3, the day fixed for elections.  Railway transportation in the province is almost non-existent owning to dynamiting of bridges, destruction of tracks and attacks on trains.  Motorbuses, which are prohibited by the Army from circulating after 5 P. M., are being attacked during the day.  Trucks transporting merchandise are captured and carried off or burned.  Groups of vehicles being convoyed by military forces are attacked and soldier chauffeurs killed even on the Central Highway, which runs the length of the island.  Telephone, telegraph and power lines are being destroyed and many times the poles and cables are carried off by the rebels.  Telephone and telegraph communication from Havana to Santiago de Cuba, capital of Oriente Province, has been cut off for days at a time.

Several weeks ago Castro sent an armed column of 400 seasoned fighters to Camaguey Province and Las Villas Province.  Under Major Che Guevara, an Argentine doctor and aide to Castro, and Major Camilo Cienfuegos, two columns fought their way across Camaguey in Las Villas, Cuba's central province where the "Directorio Revolucianario" composed mainly of Havana University students, has been fighting for months.  Che Guevara is said to have taken command of the rebel operations there.  Apparently it is Castro's intention to cut off all transportation between the capital of Havana and the three eastern provinces which feed Havana.

There is not doubt that Castro's forces are better versed in guerrilla warfare than the Government troops.  Batista has incorporated into his armed forces of some 40,000 men, 10,000 new recruits who are given a couple of months training but are no match for Castro's veteran guerrillas.  Throughout the island these troops are known as "bocaditos" or appetizers.

In Oriente Province Castro is imposing taxes on the sugar and coffee industries and commerce.  Sugar mills operating in Oriente, Camaguey and Las Villas provinces have been notified by the rebels that they must pay 15 cents per bag  of 250 pounds of raw sugar.  The Batista Government recently imposed an additional tax of 10 cents per bag of 250 pounds of raw sugar to help pay the cost of fighting the rebels.

There is no indication as to what will happen during the coming months.  If the Presidential candidate of Batista's Government coalition wins in the election tomorrow, as is expected by all observers, the rebellion will continue.  Castro has sworn to overthrow Batista or any new government elected under Batista's rule.

Of Cuba's six provinces, only Matanzas and Havana are free of rebels.  Castro has said that his revolution is being developed by "stages" and that eventually he will capture the entire island.  That is a possibility for the future.  But so far the armed forces, which have been a decisive factor in this country's political life, have remained loyal to Batista.