The Deutsche Bank, West Germany's largest bank, has expressed interest in purchasing the billion-dollar World Trade Center from the Port Authority of New York & New Jersey.

Both parties said talks are still in the preliminary stages. But they indicated the negotiations are serious about possibly transferring ownership of all or part of the 110-story twin office tower complex that dominates the lower Manhattan skyline.

'I think it's a serious, considered approach, and they clearly did their homework before they came in." said Peter Goldmark, executive director of the public agency that owns and operates the World Trade Center.

"This was not an idle inquiry on their part," he added. "We have by no means reached a conclusion that we're interested in selling it, but we're intrigued."

Goldmark said the approach was made several months ago and that a meeting was held in New York in mid-August. "The bank did the talking and we did the listening," he added, indicating the Port Authority is waiting to hear more from the German Bank.

The Deutsche Bank - which ranks third in size in the world after Bank of America and Citibank, with deposits topping $60 billion - emphasized that it is interested in the World Trade Center as a possible investment for clients whose funds it manages, and not for itself.

'We're definitely not acting on our own behalf," said Ferdinand Krier, vice president of the Deutsche Bank's New York branch.

He said his bank "is interested in, and continues to be interested in, good, solid real estate investments in this country," and noted that it already has purchased parts of the Pennzoil and Shell Oil buildings in Houston on behalf of clients.

What degree of profit and yield the big German Bank could expect on such a real estate investment is debatable. When the giant complex, with more that 9 million square feet of office space, opened in 1972, it was considered something of a white elephant because of a general glut of office space in New York City that has taken more than five years to absorb.

When the complex opened, the twin towers were the highest buildings in the world at 1,350 feet, topping the 1,250-foot Empire State Building. However, the height record now belongs to the Sears Tower in Chicago which, while also 110 stories, measures 1,454 feet.

Initial tenants of the Trade Center were primarily New York State agencies, which still take in about $84 million in operating revenues this year, but would account for one-third of all the space in the complex. Occupancy, however, has reached 90 percent, and the two skyscrapers and several adjoining structures are expected to be 100 percent rented by the year-end, according to Goldmark.

"But even if we are fully rented, we would still not be paying our debt service cost," the executive director of the Port Authority observed. He said the center would take in about $84 million in operating revenues this year, but would fail short of paying debt service costs and other expenses by "about $5 million."

The long-term outlook for the center over the next 10 to 15 years "looks very solid and attractive," Goldmark observed. He said this is why the Deutsche Bank is interested. "The fixed investment is already all there, and operating and maintenance costs are not going to escalate very much. This place is going to make money, though I don't know when we cross that line or how much that will be," he said.