President Trump and Prime Minister Starmer will put the historic Anglo-American  “special relationship” to one of its severest tests Thursday when Sir Keir meets Mr. Trump at the White House and tries to talk him into standing up for Ukraine.

That goal won’t be easy considering that Mr. Trump has called the Ukrainian president, Volodymir Zelensky, “a dictator” and refused to support a United Nations resolution condemning Russia for the invasion on the third anniversary of the Russian invasion.

The British premier, however, arrives just as Mr. Trump and Mr. Zelensky are talking about an agreement under which America would get about $500 billion worth of Ukraine’s natural resources, including rare earth and other minerals that are vital in the electronic age.

Mr. Trump sees America acquiring those riches as a great way for Ukraine to pay off the billions of dollars’ worth of arms that Washington has poured into the war effort. Mr. Zelensky has said that’s way too much for a country whose annual gross domestic product hovers at around $900 billion. He may, though, be open to compromise — all in keeping with  Mr. Trump’s zest for deal-making.

In that spirit, no sooner will Messrs. Trump and Starmer be done exchanging handshakes and smiles than Mr. Zelensky should be on his way to Washington. Having said that Mr. Trump lives “in a disinformation space,” he may still see the president on Friday. Could they somehow come to terms on the $500 billion figure, which Mr. Zelensky could reconsider if Mr. Trump can promise not to stop the flow of the arms needed to prosecute the war?

That won’t be at all easy considering that Mr. Trump, in a lengthy phone call with President Putin, promised to work with him to stop the war. Following up, Secretary of State Rubio chatted for more than four hours with Russia’s foreign minister, Sergey Lavrov.

Mr. Zelensky has so far been left out of the talks. That’s more than hurtful — it could signal the end of his presidency, from which he’s said he would resign if only Ukraine could join the North Atlantic Treaty. That’s not going to happen as long as Washington is negotiating with Moscow on Ukraine, but here’s where Sir Keir enters the picture.

The prime minister may impress on Mr. Trump the concept of a peace-keeping force to which Nato nations would contribute arms and men as needed to enforce any agreement. The payoff for Russia would be permanent control over territory it has already seized from Ukraine — the eastern and southeastern Donbas region and Crimea, the southern peninsula that juts into the Black Sea — and an end to sanctions.

Mr. Starmer, since becoming prime minister last July, has been a strong advocate of the NATO role in Ukraine but might envision a peace-keeping force that did not fly the NATO flag and did not include American troops. Nor surprisingly, Moscow has indicated it is not going for a deal that calls for troops from any country but Russia — and presumably its North Korean ally — to remain on Ukrainian soil.

Mr. Trump may balk at an agreement that Russia doesn’t want to sign, but Mr. Starmer may tell Mr. Trump, here’s a way to fulfill his demand that European countries contribute their fair share to the defense of Europe. The prime minister is already calling for his own government to increase its defense spending to 2.5 percent of Britain’s GDP last year of $3.4 trillion, up from 2.3 percent.

Putting on a show of traditional Anglo-American friendship, Mr. Starmer and his ambassador to Washington, Lord Peter Mandelson, will have to swallow some old comments that were not at all complimentary.  

Mr. Trump should have a few other topics to discuss ranging from trade and tariffs to Britain’s agreement to turn over the Chagos Islands in the Indian Ocean to Mauritius, the island nation off Africa more than 1,000 miles away.

As our Benny Avni reported, the Chagos Islands agreement has infuriated the Trump administration. The British assure Washington that a 99-year-lease would guarantee the American grip on its strategic American base at Diego Garcia, but the White House reportedly is wary of any deal that opens the way for Communist China to extend its tentacles ever more deeply in the region.