The formation of unified national zimbabwe Army from three separate and atagonistic forces is proving to be the most difficult and sensitive task of Prime Minister Robert Mugbae's postwar reconstruction program.

The extent of the progress so far in joining these forces depends on whom one asks and which yardsticks are applied. The merger appears to be going better than many observers had predicted, but slower and more precariously than the country requires.

Unifications of the former white-run Rhodesian government forces with the guerrilla armies of Mugabe and his guerrilla partner Joshnua Nkomo is necessary to give Mugabe an organized and reliable force to support his government. It is also urgently needed to defuse the increasing dissatisfaction of some 30,000 inactive former guerrillas who have been in 14 holding camps across the country since January.

A united Army is also required to back up police in their efforts to cope with a serious disruption of law and order in a country widing down from a seven-year guerrilla war. Apart from creating security for both blacks and whites, the government anxious to provide stability to encourage foreign investment.

The seriousness of the security situation was underscored today by the Parliament's six-month extension of special emergency laws that have been in force for 16 years for deal with unrest. Under them, police are allowed to detain people without charges.

Speaking in Parliament today, Home Affairs Minister Nkomo attributed the "state of lawlessness in the country" to dissidents" whom he described as former guerrillas who have "no loyalty to any political party or to the government." They have to be "rounded up and punished for their crimes," he said.

Another "source of trouble" is former guerrillas who temporarily leave their camps. "I understand their frustration at having been in the assembly places for so long but I cannot condone their actions in the surrounding areas, which undermine public safety and security," he said.

Nkomo also said the members of both his and Mugage's political parties are involved in violence against members of the rival party. "This cannot be allowed any longer," he said. The fact that he did not make specific accusations against Mugabe's followers is seen as a sign Nkomo is supporting Mugabe's policy of reconciliation.

The delicacy of molding the three armies into one force was hightlighted last week by the decision of Lt. Gen. Peter Walls to leave his post as chairman of the Joint High Command.

Former commander of the Rhodesian forces, Walls had been asked by Mugabe, who is also defense minister, to oversee the merger process, which was scheduled to be completed by the end of this year.

Walls said publicly his early retirement had nothing to do with the problems of merging the forces, but military sources close to the 54-year-old commander said his frustration at how the exercise was going and political statements by some of Mugabe's more outspoken ministers were reasons for his decision.

Walls was particularly upset by public attacks on Nkomo from Mugabe's minister of finance, Enos Nkala, and minister of manpower Edgar Tedkere. Those remarks impeded Wall's efforts to foster non-political attitudes among the young ex-guerrillas being trained for the new Army. They led to increased antagonism between two different guerrilla groups that are largely drawn from rival tribes in Zimbabwe, the source said.

When mugabe failed to repudiate the ministers publicly, Walls became uncertain whether Mugabe santioned their remarks or not, the sources said.

Walls was also reportedly angered by remarks made by some ministers to followers that whites would only be used until they were no longer needed. those comments led walls to the conclusion that Mugabe's reconcilation policy was intended to last only until he had consolidated enough power to implement a one-party marxist state, the sources said.

The commander was also worried about the high resignation rate among whites in the former Rhodesian Army, which government sources say is more than 60 percent. Most of these resignations will take effect in September, and could result in the collapse of the logistical and administrative structures on which the new consolidated army is based, the sources pointed out.

In addition, Walls was reportedly frustrated by the lack of complete authority that he formerly enjoyed as supreme commander of Rhodesian security forces because of Mugabe's decision to maintain the separate command structures of the three armies until the merger is complete.

That was done to avoid resentment from any of the three forces. "We don't want to push so hard because then people will say we are pushy because we are the government" said a senior Cabinet minister, discussing the problems of the merger. "We want it to be seen as a national effort." he added.

Wall's departure leaves Mugabe with the difficult decision of finding a replacement, who is reportedly to be chosen from a Commonwealth country.

But all is not bleak in the consolidation effort. The training of the merged forces is now in full swing under 85 British military instructors who are here at Mugabe's request. When the British contingent rises to 130 instructors in October, it will be the largest overseas British training group anywhere.

The first fully trained merged officer corps will finish its four-week course next week and then be assigned to the first properly trained battalion of 1,020 men. plans call for merged infantry battalions to be formed at the rate of one every two weeks after that until there are eight or nine such battalions. they are to absorb some 10,000 of the former guerrillas. The government hopes to attract the other 20,000 into a form of paramilitary service in huge agricultural projects.

Another hopeful sign is that an experimental battalion formed before the present training structures were set up performed reasonably well when it was recently sent out to help police round up dissidents, according to Western diplomatic and military sources.

In addition, while white resignation from the former Rhodesian Army clearly indicates low morale there, it is reportedly not a totally demoralized force. One high military source said that whites in the elite Special Action Forces were enthusiastic about their job, "probably because they have accepted they will be an integrated unit," he said.

In contrast, whites in the all-white elite Rhodesian Light Infantry unite were among the most despondent, because they had not adjusted to the fact the force cannot remain all white. He said he expected most unit members would resign by the end of the year.