Syria's President Hafez Assad is the only Arab leader who will meet President Carter half-way instead of journeying to Washington - an indication both of the pivotal role he and Syria play in the Middle East and of his strong independent streak.

He is emerging as a powerful statesman in the Middle East game of nations.

"When Assad meets President Carter, he will do it as a strong man running a strong country," a Western, non-American diplomat said here in an obvious reference to the economic chaos that bedevils Egypt's President Anwar Sadat.

While Assad has supported Sadat publicly, close associates revealed that privately he thinks the Egyptian leader has been too optimistic and staked too much on the chances of the peace drive's succeeding and has overestimated the U.S. influence over Israel.

Moreover, they say, he thinks that Sadat has already made too many concessions without getting anything from the Israelis in return.

For those reasons, Assad is believed unlikely to come up with any new proposals during his talks with Carter in Geneva Monday. But his agreement this past week to a narrow demilitarized zone on both sides of the Syrian-Israeli border - providing the secure boundaries that Israel demands and that President Carter has said it should have - was designed to show that he also can be flexible.

Over the years Assad has displayed a sophisticated skill in dealing with various issues. He has managed to force the Kremlin to renew its strained ties with Syria on his terms; become increasingly friendly with the United States; gained control over the Palestinian movement; maintained the peace in neighboring Lebanon; and balanced the desire for an end to hostilities with Israel with a refusal to make concessions until some are offered to him.

Amid all this, this little country is gaining political stability. Despite assassinations of at least 20 of his supporters in the past 15 months by political and religious opponents on the left and right, most observers here believe that Assad is firmly in control.

He has been in power for seven years, a record for this country, where a coup occured almost every year between its independence in 1946 and Assad's takeover in 1970.

Moreover, most experts, including a number of American bankers who visited here this spring, believe Syria's long-term economic future to be bright, even though it is now expriencing rampaging inflation and a foreign-exchange crisis.

As an indication that Syrians have faith in their country's economic and political future, the population has risen from 6 million to 8 million in the 1970s after 20 years of remaining steady.

The country has enough good farm land to support as many as 30 million, and the government is concentrating on improving agriculture. In contrast, Egypt, with very little good farmland, has a population of 40 million.

It is almost impossible to conduct an interview here - whether with diplomats, government officials or well-placed Syrians - without hearing Syria's strengths compared to Egypt's weaknesses.

While not there yet, Syria clearly is aiming for the leadership role of the Arab world that traditionally has been Egypt's.

Without the large population of Egypt or the oil riches of Saudi Arabia is achieving leadership by adopting a serious approach to its relations with foreign and Arab governments, appreciating the uses of power, and utilizing its strategic location bordering Israel, Jordan, strife-torn Lebanon and extremist Iraq.

The feverish diplomatic activity nowadays involving Syria underlines its new position in the world.

Three weeks ago Assad visited Moscow and then dispatched his foreign minister, Abdel Halim Khaddam, to Washington. Two weeks ago, David Owen, the British foreign secretary, visited Damascus and this week Assad received visits from high Kenyan officials and Austrian Prime Minister Bruno Kreisky, Syria's independent spirit has angered Saudi Arabia, which bakrolls much of the non-oil Arab world, especially when editorials and interviews by Syrian government officials accuse the oil-rich Arab states of stingness.

But there seems little that Saudia Arabia can do except tighten its purse strings some more. In fact, promised Saudi payments that have never been delivered are the mayor cause of Syria's foreign-exchange crisis. Last year, Syria had a $400 million trade deficit and belt-tightening measures have been been taken to try to improve the situation.

One economic expert here said, however: "Syria can survive without Saudi payments, Egypt cannot."

Sadat has taken the lead in the Arab powers' six-month-old peace offensive, proclaiming 1977 as the year to start serious negotiations and asserting that the United States has the clout to pressure Israel into concessions.

Assad has also shown flexibility in his willingness to recognize the existence of Israel.

"For more than 20 years," said his press secretary, Assad Elias, "the Arabs said no to the existence of Israel. Now we say all right. The Palestinians say it, too."

While other Arab capitals see Assad's refusal to go to Washington, especially after just returning from Moscow, as a snub to the United States, government officials in Damascus have gone to great pains to insist that this is not so.

"If Assad went to Washington, it would mean that SYria is the only one of the two countries interested in the meeting," explained Ahmed Iskander Ahmed, Syria's information minister.

"This way, it shows that the United States is also concerned, so they are coming to each other. It is a symbol of improved relations between the two countries. President Assad would like to go to Washington, but it would be better under different conditions."

Syria broke off diplomatic relations with the United States after the six-day Arab-Israeli war in June 1967 and resumed them only in 1974, when President Nixon visited Damascus. Since then, relations have steadily improved, but there is still some suspicion here of U.S. intentions in the Middle East.

Leftists in the ruling Baath Party, for example, oppose closer ties with the United States; Assad, considered a moderate, must be careful not to alienate them too much, diplomats here said.

These leftist Baathists are believed to be responsible for some of the political killings in Syria. There is also a resurgence of Moslem orthodoxy - illustrated by the crowded mosques on Fridays - that runs counter to the minority Alawite wect that runs the country.

Assad is an Alawite, as are most of the leaders of the government and the army, and many Moslems - especially Sunnis, who comprise a majority of the country - do not believe that Alawites are true followers of Islam.

So, while political and sectarian opposition have buffeted Assad's regime, most observers here do not think his government is threatened. He was able to survive an unpopular conflict in Lebanon, where Syrian troops fought Palestinians they had once befriended, despite the great economic disruption the war caused in Syria.

Assad is so confident of his position that last month he released more than 200 political prisoners, most of them pro-Iraqi extreme leftist Baathists.