Minnesota's congressional delegation sent a letter Friday to U.S. Transportation Secretary Anthony Foxx asking him to help Delta Air Lines fly from Minneapolis-St. Paul International Airport to Tokyo's close-in Haneda airport.

The letter is the latest move in a battle to keep Delta, a major state employer and MSP servicer, competitive in international travel.

The Japanese are opening some coveted daytime landing slots at Haneda airport to U.S. airlines.

Delta now flies from Minnesota into Tokyo's Narita airport, which is about an hour outside the city. Delta has claimed that its hub at Narita is threatened by the expansion of Haneda, because it will force it and competitors to split their service. The airline's MSP-Narita flight would be one of those at risk. Delta asked for three of the five new slots at Haneda and its executives said they put a priority on making a flight from MSP for one of them.

"Allowing service between MSP and Haneda is now imperative to maintaining Minnesota's connection to Asia," the delegation's letter stated. The group said that losing a direct flight to Asia would hurt the state's economic competitiveness.

"Access to growing Asian markets is particularly important to Minnesota businesses, including the 17 Fortune 500 companies headquartered in our state," the letter said. "In 2015, employees from just 25 businesses in Minnesota took more than 10,000 flights from Minneapolis/St. Paul to Tokyo."

Senators Amy Klobuchar and Al Franken signed the letter, along with Representatives Betty McCollum, Collin Peterson, John Kline, Tim Walz, Keith Ellison, Erik Paulsen, Rick Nolan and Tom Emmer. The senators and representatives also cited a Delta plan to make MSP a connecting hub for travelers from 114 U.S. cities to reach Tokyo.

A Transportation Department decision about who gets the daytime slots at Haneda is expected in the next few months. Other U.S. carriers, United Airlines, American Airlines and Hawaiian Airlines, also requested slots at Haneda.