U.S. Defense Secretary Mark Esper said on Monday he called South Korean Defense Minister Jeong Kyeong-doo to discuss the importance of an "equitable" defense cost-sharing agreement between the allies.   

Esper tweeted that he appreciates Minister Jeong taking his phone call to discuss the importance of equitable burden sharing across the alliance, stressing it's critical that they get a "fair, balanced, and comprehensive agreement signed quickly."

He then added the alliance's motto, "#KatchiKapshida," which in Korean means "Let's go together."  

Seoul and Washington have held seven rounds of negotiations since September, but have yet to reach agreement on how to share the costs for the upkeep of 28-thousand-500 American troops stationed in South Korea. 

The phone call took place days after U.S. Forces Korea placed thousands of Korean workers on U.S. military bases on unpaid leave, citing the absence of an agreement to cover their salaries.