His decision-making was aimed at avoiding anything "that will drive, foolishly, Russia away from the bargaining table".
He also mentioned "current hostage negotiations", apparently referring to prisoners held by the warring sides, but gave no details.
The Wall Street Journal is reporting that Russian President Vladimir Putin has proposed a November summit with Trump and Chinese leader Xi Jinping to negotiate an end to the four-year conflict that will favour Moscow.
Citing a former Russian intelligence officer, the paper said Putin's suggestion came in an October 9 telephone call with Trump that also yielded a deal for the US to buy Russian diesel and facilitate its sale on the global market.
The US has yet to achieve a breakthrough towards ending the war and Trump now faces accusations of neglecting Ukraine as he focuses on the conflict with Iran.
Trump said Russia was doing "very little, if anything, to help the Islamic Republic of Iran", and he wanted to keep it that way.
Trump also accused Ukrainian President Volodymyr Zelenskiy of not wanting to end the war.
Zelenskiy "doesn't want to end this war, and probably never did", he wrote.
Trump criticised strikes on Russian diesel refineries, blaming Ukraine for a global diesel shortage. Critics accuse him of trying to distract from the consequences of the Iran war.
Ukrainian strikes set an oil export terminal and a depot ablaze in St Petersburg after launching more than 1000 drones at Russia on Sunday, in one of its largest aerial attacks of the war.
One person was killed and five others were wounded in the St Petersburg attack, which sparked fires at the Petersburg Oil Terminal and the city's Ruchi oil depot, Governor Alexander Beglov said.
Russia's defence ministry said its forces had destroyed 1015 Ukrainian drones over 15 Russian regions, the annexed Ukrainian peninsula of Crimea and the Black Sea.
Fuel prices have risen sharply since the start of the Iran war, putting Trump under pressure ahead of the November congressional elections.
Trump praised Russia for exporting millions of barrels of diesel at low prices. About a week and a half ago, he unexpectedly announced Russia would supply hundreds of thousands of tonnes of diesel to global markets.
Washington temporarily suspended sanctions on Russian fuel, while Moscow partially lifted its diesel export ban.
Meanwhile, Zelenskiy revealed the US had resumed providing Ukraine critical intelligence to help it defend against Russian missile strikes, after a brief pause.
Ukraine has relied on US intelligence to spot the fast-moving ballistic missiles that Russia has fired in waves at its cities.
Trump had said that Washington was still sharing intelligence, although Ukrainian officials said some Russian strikes had occurred without warning.
Speaking to NBC's Meet the Press, Zelenskiy said intelligence-sharing had been interrupted but later "de-blocked".
"We are very thankful for this," he said.
But Zelenskiy said the US signing a deal to import Russian diesel and waiving sanctions on Russia would hurt Ukraine.
"If the United States will officially take the side of Russia, of course if these two countries will be together, of course we will not prevail and we will not be able to stand," he said.
Zelenskiy told NBC he hoped Trump would remain an ally of Ukraine.
"We want to trust him, and I hope that he will change his decisions," Zelenskiy said.
with Reuters
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