Trump told the Washington Post he was waiting on a "full report" on the maritime dispute during which Russia fired at and captured three Ukrainian vessels on Sunday.
“I’m getting a full report on that tonight. That will be very determinative. Maybe I won’t have the meeting. Maybe I won’t even have the meeting. We’re going to see, depending on what comes out tonight,” he said.
The leaders were set to meet later this week during the G20 summit in Buenos Aires.
How did the clash unfold?
Russia fired at and captured three Ukrainian vessels at sea on Sunday — a move the West fears could ignite a wider conflict.
It happened near to Crimea, which Russia annexed from Ukraine in 2014. The West and Kiev have always condemned the annexation and said it was a violation of international law.
At least 12 of the Ukrainians have been detained for 60 days, thanks to a Crimean court's ruling. Decisions concerning the remaining servicemen were exected Wednesday.
The FSB, Russia's principal security agency, released videos of some of the servicemen making statements.
One of the men, Andriy Drach, said: "We were warned by the border service of the Russian Federation that we were violating Russian law. They had repeatedly asked us to leave the territorial waters of the Russian Federation."
Ihor Voronchenko, Ukraine's navy commander, said the men were made to give false statements under duress, according to Ukrainian TV.
EU politicians consider sanctions
Several senior European politicians raised the possibility of new sanctions against Russia.
The United States also now seeks a tougher European stance against Russia over Ukraine.
"Many governments have imposed sanctions on Russia for its actions in Crimea, in Ukraine.
"Not all of those sanctions ... have been fully enforced. So that is one thing that we can look (at) for European countries to do more," said Spokesperson for the United States Department of State Heather Nauert.
"Also, something we've talked about a fair amount is Nordstream 2," she added.
A Russian minister told Reuters, that further sanctions would not solve anything.
Russian President Vladimir Putin spoke to German Chancellor Angela Merkel on the phone on Monday and said that Moscow was ready to provide more details of the incident and blames Kyiv for the provocation.
Merkel also spoke to Ukraine's President Petro Poroshenko on Monday and called for de-escalation and dialogue.
France’s Foreign Minister, Jean-Yves Le Drian said: "I told Sergei Lavrov that a gesture is expected from Russia, that the prisoners and the boats being held must be freed as soon as possible, but I will also call my Ukrainian counterpart to encourage him to seek a de-escalation in this region."
However, Russian Foreign Minister Sergei Lavrov said: "If the Ukrainian side, like its partners in Europe, is interested in avoiding such situations in the future, it is obviously necessary to send a signal to Kyiv not to allow such provocations.
"That is not for us to do but for those who maintain close contact with the Ukrainian authorities."
Family of a wounded serviceman speaks out
Meanwhile, the father of a 27-year-old wounded serviceman said on Tuesday he did not know where his son was.
Viktor Soroka said in the interview with Radio Free Europe/Radio Liberty that his son Vasyl was on the "Berdyansk" vessel — one of three military ships seized by Russia on November 25.
"Yesterday, Vasyl got an opportunity and he called to his wife Iryna and said a few sentences, that he is alive, healthy, his legs and hands are okay," Soroka said.
"That's it. He even didn't congratulate her on her birthday she had yesterday. I think he only said what the FSB (Russia's Federal Security Service) allowed him to say."
A reporter asked him: "Do you know what kind of injuries he sustained?"
"No, I don't know. I only know he is wounded and had surgery. I don't know anything else," Soroka replied.
What Russia says
Konstantin Kosachev, Chair of the Russian Foreign Affairs Committee of the Federation Council, said: “There will be an investigation, there will be trials because we are talking about a violation of the current Russian legislation.
"It is for this reason that the crew was detained and arrested.
"As a citizen of the Russian Federation, I would prefer that the crews return to Ukraine."
He went on to say: "There are no attempts by Russia to block the Strait of Kerch, no attempts by Russia to achieve any one-sided militarisation of the Sea of Azov in its favour.
"It is completely obvious that if Ukraine, either by itself or with the help of its allies, somehow tries to resolve issues by military means, this will all turn into a military defeat."