More than 20 Americans are missing in action on Ukraine’s frontlines, with casualties surging over the past six months as foreign troops step in to bolster the country’s struggling army, according to a CNN investigation.

At least five American fighters who joined the Ukrainian military have been killed in action in the past six months, but their bodies could not be recovered from the battlefield. Two of them were finally repatriated on Friday after prolonged negotiations.

Accounts from their surviving comrades, along with the rising casualty count, highlight the critical yet largely unrecognized role of American fighters in the war—one that President Donald Trump has dismissed as "ridiculous" while urging Russian President Vladimir Putin to negotiate an end to the war.

The intensity of combat along Ukraine’s eastern front has left many fighters' remains scattered across the battlefield, reportedly making recovery efforts extremely difficult.

Two American soldiers were killed in a single incident near Pokrovsk in eastern Ukraine in late September, according to witnesses and relatives. Their bodies have yet to be recovered. Former US soldier Zachary Ford, 25, from Missouri, and another American fighter known only by his callsign "Gunther", were killed by a drone while attempting to destroy a bridge near the village of Novohrodivka.

Trump to Putin: End 'ridiculous war' in Ukraine 

Last week, US President Donald Trump warned that he will impose steep tariffs and additional sanctions on Russia if Vladimir Putin does not end the war in Ukraine.

In a post on his social media platform Truth Social, Trump stated that by pushing for a resolution to the conflict, he was doing "Russia and its president a very big favor."

Trump had earlier claimed he could negotiate a settlement to Russia's full-scale invasion, which began in February 2022, "in a single day."

In response to the threat of intensified sanctions, the Kremlin emphasized its willingness to engage in "an equal dialogue, a mutually respectful dialogue."

"We're waiting for signals that are yet to arrive," stated Dmitry Peskov, spokesperson for President Vladimir Putin.

He remarked that Russia does not find Donald Trump's threat of additional sanctions to be anything new, adding, "He likes these methods, at least he liked them during his first presidency."

Putin has repeatedly expressed his readiness to negotiate an end to the war, which began in 2014. However, he insists Ukraine must accept Russia's territorial gains, which currently account for about 20% of the country’s land. Additionally, Putin rejects the idea of Ukraine joining NATO, the Western military alliance.

On Tuesday, Trump told a news conference that he would be speaking with Putin "very soon", suggesting that more sanctions were likely if the Russian leader did not agree to talks.

The following day, Trump took to Truth Social, saying, "I'm going to do Russia, whose economy is failing, and President Putin, a very big FAVOR. Settle now, and STOP this ridiculous War! IT'S ONLY GOING TO GET WORSE. If we don't make a 'deal', and soon, I have no other choice but to put high levels of Taxes, Tariffs, and Sanctions on anything being sold by Russia to the United States, and various other participating countries."