U.S. military efforts to recover the remains of fallen troops from North Korea have been halted after a breakdown of diplomatic talks between the two countries’ leaders.

In a statement provided to Reuters Wednesday, Defense POW/MIA Accounting Agency spokesman Lt. Col. Kenneth Hoffman said no talks on the work have taken place with North Korean military officials since February, and “we have reached the point where we can no longer effectively plan, coordinate, and conduct field operations in (North Korea) during this fiscal year.”

The return of fallen American troops’ remains by North Korean officials was the most visible result of the June 2018 summit between President Donald Trump and North Korean leader Kim Jong Un. Veterans groups hailed it as a long-overdue move in fulfilling the Defense Department’s promise to bring all missing service members home.

More than 35,000 Americans died on the Korean Peninsula during the war between North and South Korea. Of those, 7,700 are still listed as missing in action, with 5,300 believed to be on North Korean soil.

Last July, on the 65th anniversary of the armistice that ended hostilities in that conflict, military officials under Kim’s orders turned over to United Nations officials 55 cases of human remains believed to be U.S. troops.

Days later, those cases were officially repatriated into the United States in a military ceremony oversee by Vice President Mike Pence. DPAA officials have spent the last year studying the remains, and have made identifications of at least six missing U.S. service members.

Advocates had hoped that work was just the start of a broader recovery effort in North Korea. From 1990 to 2005, 229 fallen troops were identified and returned home in joint operations between the two countries. But diplomatic fights between the countries’ leadership ended that work 14 years ago.

In February, Trump and Kim met for a second summit, but walked away without any new agreements. DPAA officials said since then they have been unable to move ahead with any new recovery efforts.

Hoffman told Reuters that the department is “assessing possible next steps in resuming communications with (North Korea) to plan for potential joint recovery operations during fiscal year 2020.”

More than 82,000 Americans who fought in wars overseas are classified as missing in action. Of those, about half are believed to have been lost at sea.