The Turkish invasion in 1974 has left this island so completely partitioned that it is impossible even to make a telephone call across the line separating the Turkish and Greek Cypriot sectors.

But two recent developments have provided new impetus for efforts to end the 2 1/2 years state of war on this strategic Mediterranean island dividing Greece and Turkey.

Last month, Cypriot President Makarios and Turkish Cypriot leader Raul Denktash met for the first time in 14 years, to begin negotiations toward reuniting the island. The talks are to continue this weekend.

In addition, President Carter, as one of his first foreign policy moves upon taking office, named Clark Clifford as his special emissary to Cyprus to aid in the peace effort.

The most difficult issues blocking a settlement are the proportionss of territory to be controlled by the rival Greek and Turkish sides and the numbers of refugees that will be allowed to return to their homes, diluting the just-achieved ethnic separation.

Beyond territorial adjustments, Greek and Turkish have vastly different ideas of how this mythological island of Aphrodite should be governed.

The 1974 Turkish invasion, which followed a Greek-led overthrow of the government of Archbishop Makarios, has left the rich northern third of the island, including part of the capital's old walled city in Turkish hands.

The Rurkish army, 30,000 strong on the island, protects and administers 120,000 Turkish Cypriots, a one-fifth minority here who felt they were underprivileged and culturally victimized by the Makarios government and the Greek Cypriot majority.

Only diplomats, U.N. peacekeepers, journalists and a few hundred Maronite Christains are allowed to move from one sector to the other through the single crossing point.

The Greek sector is governed by the same administration that ran the entire country before the invasion. The Turkish Cypriots proclaimed their separate government two years ago separate government two years ago but have refrained from formally declaring independence.

Turkish officials and technicians have been sent here to "Turkify" their Cypriot cousins. Thousands of mainland Turks have settled here to boost the Turkish population of the island.

To achieve complete ethnic separation, the Turks have continued forcing out Greek Cypriots from the north. At least 150,000 Greek Cypriots left the area during the fighting and the 20,000 who remained under Turkish control at the cease-fire are being up rooted.

The Turkish Cypriots, who comprised approximately 18 per cent of the island's population at the time of the 1974 war, occupy 36 per cent of the land , roughly the northern third. The standing Turkish offer is a withdrawal to just under a third of the island.

Makarios indicates privately that at least 80,000 of the 150,000 Greek Cyproit refugees must be allowed to return to their homes. Denktash indicates this matter is "negotiable".

The Turks very deliberately advanced to position on high ground that allow them to dominate the Greek-held flatlands. Diplomats here agree that Turks are unlikely to pull back from these commanding positions.

Turkey has not settled the abandoned but thoroughly looted port and resort city of New Famagusta, once the Miami of Cyprus.

If New Famegusta, on the dividing line, were returned to Greek Cyriot control, it could accomodate 40,000 of refugees, including a hard core who are loyal to extreme rightists and a continuing problem to the moderate Makarios.

The Turks have indicated a willingness to return bits of land but these amount to only 5 per cent of the island. Turkey contends that the apportionment should not be made on the basis of population but on the basis of previous land ownership and it recently produced titles indicating 32.8 per cent of Cyprus was in Turkish Cypriot ownership before the invasion.

Greek Cypriot officials indicate privately that they intend to recover enough territory to reduce the Turish zone below 30 per cent of the island.

An outside possibly to close the numbers gap that some diplomats here are considering involves turning over two large British bases - in effect little suburban towns - to the Greek Cypriots as part of a final settlement. These bases cover 100 square miles - 3 per cent of the island. The financially strapped British would like to pull out.

Cypriots on both sides of the line say that an independent, reunited Cyprus is better than partition of the island with each sector becoming part of its motherland.

"We don't want to become the most remote province of Greece," said one Greek Cypriot. Turkish Cypriots say they are beginning to realize that Turkey acted here in its own interests, not theirs.

The Greek government of Premier Constantine Karamanlis has backed away from any plan to annex Cyprus. But the Turkish authorities appear less willing to committ themselves to any blueprint for an eventual restoration of Cypriot independence.

Both sectors of the island presumably would be under a single federal government in any settlement. The sticky questions revolve around how strong the government would be and how much freedom of movements there would be between the zones - in effect, whether the restored unity would be a reality or a facade for de defacto partition.

Makarios government demands stronger federal authority. While they quietly acknowledge Turkish Cypriots must now have their own internal security, Greek Cypriot officials insist the government must be powerful enough at least to insure the island's economic unity and control further immigration that could change the island's ethnic balance.

To demonstrate true freedom of movement, Makarios wants any agreement to guarantee the Greek Cypriot refugees' right to return to their homes in the north and work there if they wish. In practice, most would settle for compensation.

Western aid has already fueled a remarkable economic recovery in the Greek-controlled sector. Turkis Cypriots get their pro rata share of U.S. aid, funneled through the U.N. High Commissioner for Refugees, but it has had less visible impact in their sector.

The Makarios government has managed its aid well - $75 million since 1974 from the United States, making Cypriots the world's highest per capita recipients of U.S. aid. It has provided adequate housing for refugees and new jobs for all but a hard core in a reviving economy.

The recovery was helped by the civil war in Lebanon. The collapsed of Beirut as a commercial hub gave Cyprus the opportunity to expand its lucrative markets in the oil-rich Arab states.

Cypriot contractors, using Cypriot labor, have gotten all the construction projects they can handle in the Middle East.

The economy on the Turkish side has been a failure, even though the Turks in 1974 took over the most productive assets, the best citrus groves, the biggest cargo port, many modern tourist facilities and the U.S. owned copper mines, which are now idle.

The economic contrast is an inducement to Turkish Cypriots to some form of reunification and it has even spawned stirrings of restiveness with the Turkish military occupation.