The idea of connecting the No. 7 subway line to New Jersey may not be quite dead yet.

The Port Authority of New York and New Jersey is commissioning a long-term study of ways to expand the use of rapid transit across the Hudson River, and it expects to get some help from the Metropolitan Transportation Authority, which operates the subway.

The two authorities are teaming with New York City and New Jersey Transit to consider a wide range of options for increasing commuting capacity two decades down the road. This week, the Port Authority received several bids from firms seeking the contract to produce the study, said Rick Cotton, the agency’s executive director.

Mr. Cotton said in an interview on Tuesday that the notion of extending the No. 7 line — an idea that was briefly considered several years ago — was just one of many possibilities that would be analyzed. He said he had not discussed the feasibility of connecting the city’s subway system to New Jersey with any officials of the transportation authority, including its chairman, Joseph J. Lhota. Six years ago, Mr. Lhota said that a trans-Hudson subway extension was “not going to happen in anybody’s lifetime.”

A spokesman for the transportation authority, Jon Weinstein, declined to discuss the study. In a brief statement, he said, “We look forward to working with federal, state and local public sector partners and private parties to explore long-term options for trans-Hudson transportation.”