Representatives from Estonia, Greece, Latvia, Poland, Romania, Lithuania, Bulgaria, and the United Kingdom attended the lunch, according to the White House. Earlier before that reception, Trump had, according to Washington Post, turned "what were expected to be brief photo opportunities into his own personal daytime cable show".
But, despite having been only too happy to talk to the press for the two days of the meetings, he abruptly canceled this scheduled appearance.
The president's visit to London featured frosty conversations with North Atlantic Treaty Organisation leaders over their inability to reach the 2% benchmark.
Trump insisted his accommodation with Erdoğan has helped USA interests, even as it has cost the lives and territory of America's longtime allies against Islamic State, the Kurds, and helped Russian Federation bolster its power and influence in the region.
The highly choreographed anniversary gathering, meant to show unity, has been unable to hide deep differences between member states, BBC's defense correspondent commented.
Nevertheless, officials said important decisions were reached at the summit, including an agreement to ensure the security of communications, including new 5G mobile phone networks. The press conference also would have allowed members of the broader press corps to ask questions, beyond the "pool" that gets closer daily access to the president's movements and remarks.
Although the 29-member bloc's future is not in doubt, there are disagreements over Turkey's recent military action in northern Syria; the levels of military spending by members; and recent comments by Mr Macron that the alliance is "brain dead".
Johnson opened Wednesday's plenary session with an address in which he attempted to smooth over the tense relationship, by citing the motto of the literary Three Musketeers.
He told reporters: "We'll go directly back".
Johnson asked Macron, "Is that why you were late?" and Trudeau replied with: "He was late because he takes a 40-minute press conference off the top". On Tuesday, Trump vented with reporters about impeachment, Democrats and other vexations for more than two hours during his supposed private meetings with other leaders.
Trump subsequently called Trudeau "two-faced", but otherwise appeared to take the comments in stride, no doubt leaving Trudeau - and the rest of Canada - to breathe a sigh of relief the damage was not worse.
Mr Trump added he thought Mr Trudeau was a "nice guy" and was probably "not very happy" that he had been called out over not meeting NATO's two per cent spending thresholds. A lot more money is being produced by a lot of countries and they are enthusiastic about it.
Trump added: "He's not paying 2 percent and he should be paying 2 percent".
"Look, I'm representing the U.S. and he should be paying more than he's paying, and he understands it". And he understands it.