Israel in Lebanon: digging in for a long stay?

Israel's campaign to convert occupied Lebanon into a ''north bank'' has made significant headway. And international workers in the region are expressing concern about intentions of a permanent Israeli presence in Lebanon.

While Israelis at the negotiating table show a willingness to withdraw from Lebanon, their actions on the ground seem to indicate exactly the opposite, according to diplomats and United Nations sources. Recent moves include:

* Construction of an airstrip capable of handling big C-130 military cargo planes near Damour, just south of Beirut, over the past month. More recently, the Israelis have developed a small port near Giye, the sources said.

* Building of additional fortifications, from platoon bases to major logistical facilities. One well-placed envoy said he was told the Israelis felt it would now take at least two months to dismantle their military infrastructure , and then only under perfect security conditions.

* Establishment of a political and military infrastructure loyal to Israel among southern Lebanon residents, which diplomats feel will grow even faster if US-directed negotiations drag on.

The effect of these moves is to consolidate the hold of the Israelis on the north bank of the Jordan River, not loosen their grip in preparations for withdrawal.

Key Lebanese officials have begun to express concern about a ''genuine'' agreement. They fear that even if an agreement were reached, the Israelis might come up with a pretext later - such as inadequate security conditions - to delay or effectively void an accord.

The most ominous development is the growth of the pro-Israeli governing units , modeled on the ''village league'' system on the West Bank, which Israel occupied after the 1967 war. The plan was called the Organization for a Unified South when put forward last February, but has been renamed United South Assembly (USA).

Sources in south Lebanon say the Israelis have foisted hand-picked leadership on more than 40 villages. About 30 also now have ''National Guard'' militias - armed and trained by Israelis - to back up the village committees.

Resistance to the scheme was reportedly originally high, led by ''muktars,'' or traditional local chieftains of the predominantly Shiite Muslim population. But international officials in the area claim that cracks have developed because of the time factor.

''The muktars cannot hold out forever. I don't think resistance is less. But fear of the future is higher the longer the Israelis stay on, and there is no alternative for them,'' one said. ''This is one area where the domino theory applies: If one village goes, then the next one will soon go.''

Countries with contingents in the United Nations peacekeeping force in the south have also reported threats against those who resist joining the scheme.

The USA was originally interpreted as an effort to create a pro-Israeli body that would look after Israeli interests in the event of a withdrawal. But diplomats are now concerned that the plan is designed to back up, politically and militarily, a continued Israeli presence in Lebanon.

Their original role was to function as a local police force, in part to cut down manpower demands on Israeli forces. But that too has apparently been extended. Many militiamen now carry sophisticated automatic rifles and grenades, more than is necessary for police.

A recent announcement said the National Guard would take over security in the port city of Sidon next week, in coordination with the Israeli military command.

Leader Mustafa Al Gharamty claimed his force now numbers 500, but was expected to number 1,000 soon because of a rush to join. The original goal was reported to be between 5,000 and 12,000 guardsmen throughout the south, a significant force for an area less than one-fifth the size of Connecticut.

There is also now talk of an official ''territorial brigade'' that would combine these units with the forces of Maj. Saad Haddad, the Israeli-backed renegade Lebanese militia leader. This would again exceed the original statement of intent.

Both the village committees and the National Guardsmen represent a direct challenge to US hopes of returning sovereignty and territorial integrity to the Lebanese government of President Amin Gemayel.

Diplomats increasingly compare the situation with the West Bank, and attempts at de facto annexation. They also suggest that, with each week of progress for the USA, the Israelis build up more leverage for their demands at the negotiating table. One envoy predicted this week: ''Soon they will be so entrenched that no one can get them out.''