ARLINGTON, Va. — The emergence of natural gas as a viable fuel for the commercial trucking industry is a matter of when — and not if — issues such as a cost-effective fuel supply network, a new generation of engines and driver acceptance are overcome, industry experts said here Thursday.

Management and labor negotiators in the East and Gulf Coast port contract talks have agreed to a 90-day extension of a contract that was due to expire on Sept. 30, giving the two sides more time to “focus on the outstanding core issues in a deliberate manner.”

Stalled labor negotiations between the International Longshoremen’s Association and management negotiator United States Maritime Alliance will resume the week of Sept. 17, the Federal Mediation and Conciliation Service said Thursday.

LISLE, Ill. — Navistar International Corp. executives revealed their new strategy for introducing an updated product line with new emissions equipment, in a bid to recapture market share and counter competitors who have capitalized on stalled regulatory approval of Navistar’s own technology.

The National Retail Federation called on both sides involved in labor talks at ports on the East Coast and Gulf Coast to reach an agreement without a work stoppage, which would force diversions and delays of cargo.

The largest U.S. freight railroads reached a tentative agreement last week with a union representing track and bridge maintenance workers, eliminating the possibility of a nationwide work stoppage.