Just two hours earlier as he departed the White House, Trump had told reporters he looked forward to meeting with Putin during the G-20 leaders' meeting.
Speaking to reporters at the White House, he said that while China was interested in striking a deal, "I don't know if I want to do it" and "I like the deal we have now".
He will press Chinese President Xi Jinping to avert the stepped-up tariffs by throwing open China's markets to USA competition and protecting foreign companies' intellectual property.
Tensions have loomed between Ukraine and Russian Federation after the crisis over the weekend in the Black Sea and Sea of Azov. Similar speculation swirled ahead of Trump's summit with Putin in Helsinki last July, which came days after the chief investigator in the Russia probe, special counsel Rober Mueller, issued indictments of 12 Russians for interfering in U.S. politics.
Mr Trump had been reluctant to condemn Russia's latest aggression in Ukraine, and shortly before heading to Buenos Aires he said he would meet the Russian president.
The Kremlin denied it was restricting shipping, saying it had not heard of any problems.
Poroshenko's comments were published Thursday in the German newspaper Bild. He has slapped tariffs on the European Union, pulled the USA out of the landmark Paris Climate Accord and the Iran nuclear deal and suggested he might be willing to pull the US out of North Atlantic Treaty Organisation if member countries don't significantly boost their defense spending.
Russian Federation continues to hold three Ukrainian naval vessels and more than 20 sailors they seized last weekend in the Black Sea. "The incident in the Black Sea happened, it is a border incident, no more". "So there is already a lot of North Atlantic Treaty Organisation in the Black Sea, and we will continue to assess our presence in the region".
On Wednesday, the European Union expressed its "utmost concern about the unsafe increase of tensions" in the Kerch Strait and Azov Sea and called for the "utmost restraint to de-escalate the situation immediately", as well as the swift release of the seized Ukrainian ships and crew.
The following day, Ukraine's parliament voted to introduce martial law for 30 days in areas of the country deemed most vulnerable to an attack from Russian Federation.
The Russian president said the Ukrainian ships had entered Russian territorial waters and refused to respond to requests to stop from Russian patrol boats. According to the New York Times, Mueller planned to ask Trump himself the following question about the Trump Moscow project: "What communication did you have with Michael D. Cohen, Felix Sater, and others, including foreign nationals, about Russian real estate developments during the campaign?"
Since then, the United States has investigated Russia's possible interference in the 2016 election that Trump won.