FARC rebels need the United Nations to reschedule the dates for Colombia's historic disarmament process, as the country readies to implement a peace deal to end Latin America's last major armed conflict, they said Tuesday.

The Revolutionary Armed Forces of Colombia (FARC) are due to demobilize, starting March 1, with UN supervision under a peace deal with the government after 52 years of fighting.

FARC members had been planning to surrender 30 percent of their arms on March 1, General Javier Florez -- head of the military operation to demobilize and disarm the guerrillas -- told journalists earlier.

Authorities will then collect another 30 percent of weapons on May 1, with the final disarmament date on June 1, he said.

But now, "it appears a rescheduling of the demobilization process will be needed," the FARC leadership said in a letter to Jean Arnault, head of the UN mission monitoring the peace process.

Members of the FARC, Colombia's largest and oldest guerrilla group, last Saturday finished arriving at the country's 26 zones where they will disarm and eventually live.

Rebels, however, are now complaining that the disarmament areas are not completed, in terms of basic infrastructure, water, power and roads.

They are concerned that the government appears not to be keeping its word on peace process implementation.

If basic infrastructure is not ready at most zones, many say it seems premature to be concerned just about where containers for the weapons be located, to be destroyed later under UN supervision, will be.

According to the country's Office of the High Commissioner for Peace there are 6,934 armed guerrillas concentrated in the zones.