THE United States and Soviet Union are considering opening their ports and airports more widely to each others' commercial ships and airplanes. Exploratory talks opened Monday in London on a revision of the 1966 air agreement between the two superpowers. That pact now permits Pan American World Airways to fly to Moscow and Leningrad. In return Aeroflot has routes to New York and Washington. Some flights are a joint venture of the two airlines.
In the background are relaxing relations between the US and Soviet Union and the prospect of increased commerce if US barriers are reduced.
One item likely to be on the table is the desire by American Airlines to open a new route between Chicago and Moscow.
``We don't think there is currently a big enough market,'' commented a Pan Am spokesman.
Also up for discussion may be flights between Nome, Alaska, and Providenija on the other side of Bering Strait. These flights are now made on an irregular charter basis. But the US may want to see these become scheduled and extended to other Siberian cities.
Aeroflot, it is thought, might like to expand its air-freight operations in the US.
In late January, US and Soviet officials will meet in Moscow to discuss a bilateral maritime pact. Under the last such agreement, Soviet vessels averaged more than 100 port calls a month in the US, giving four days' notice of arrival. But that arrangement was suspended when the Soviets moved into Afghanistan in 1979.
At present Soviet ships must request permission to enter an American port 14 days in advance. They can only load or unload either Soviet goods for the American market or American goods destined for the Soviet Union. They cannot take on or unload cargo from or to third nations, as in the 1970s. Competing with Soviet ships
At that time, the Soviet Union had a large number of merchant ships it had either purchased or built. The vessels carried not only Soviet imports and exports, but goods of other nations, known as ``cross trade.'' One goal was to obtain hard currency, and the Soviets offered low freight rates to get the business. American shipping companies charged the Soviets with setting rates below cost.
``They were a disruptive influence,'' says Mark Aspinwall, the government affairs representative of United Shipowners of America, a Washington organization representing US-flag ship interests.
The US is expected to insist that the Soviets not engage in ``predatory'' practises should a new agreement be reached. Congress passed a law, the Controlled Carriers Act of 1978, that requires ships owned by state enterprises to charge rates that compensate for their lower costs when doing business from US ports.
In a recent speech, a top Soviet shipping official essentially confessed to earlier freight-rate undercharging. He promised that Soviets would seek membership in the ``conferences,'' that is, the international cartels that establish freight rates for liner cargo.
Since the 1970s, the Soviet merchant fleet has aged considerably. At present it consists of 2,439 vessels with a capacity of 24.5 million deadweight tons (dwt). This makes the Soviet fleet second largest in the world in number of ships, and sixth in deadweight ton capacity. The Soviets use a large number of relatively small vessels for traffic on internal waterways.
The US has only 669 vessels but a similar tonnage - 24.7 million dwt. It is 11th in number of ships and eighth in tonnage. US-flag ships carry only 5 percent of this country's foreign trade. Some imbalance noted
Under the previous agreement, Soviet ships could enter 40 American ports and US ships 40 Soviet ports. But only eight or nine Soviet ports were of any commercial use to the Americans, whereas many more US ports were of value to the Soviets.
The imbalance does not disturb the US. ``We are here to facilitate trade,'' notes a Department of Transport official.
In both the US and Soviet Union, some ports are closed to the other country - Vladivostok and San Diego, for instance.
Another question is cargo-sharing arrangements. If the Soviets buy American grain, for example, will US-flag ships get some of that shipping business, too?
At present, most US-Soviet trade consists of bulk products. Soviet vessels, for example, arrive at US ports with vodka and leave with grain or industrial materials. A new agreement would have a greater effect on general cargo transported in containers than on bulk shipments.