The visit precedes Trump's first meeting with Russian president Vladimir Putin at the G-20 summit on July 7-8.
The Ukrainian presidential office reported Poroshenko said that Trump suggested that the United States and Ukraine must expand cooperation. The Russian officials affected are Moscow's envoy for overseas Russians and chairman for humanitarian assistance in separatist-held, eastern Ukraine.
The meeting comes as the U.S. Treasury Department on Tuesday announced it would add 38 more individuals and entities to the Office of Foreign Assets Control's list of those sanctions due to Russia's actions in Ukraine. "This administration is committed to a diplomatic process that guarantees Ukrainian sovereignty, and there should be no sanctions relief until Russian Federation meets its obligations under the Minsk agreements".
Tensions between the US and Russia are high even as the White House considers scheduling a meeting with Russian President Vladimir Putin on the sidelines of next month's G20 meeting.
In addition to meeting with Trump, Poroshenko will meet with Secretary of State Rex Tillerson and Secretary of Defense James Mattis on Tuesday.
"We have no idea if [Trump] will keep his promises, because he can often change his mind overnight", one Ukrainian official who knew of Poroshenko's earlier phone calls with Trump, told reporters.
Trump has found himself on the defensive politically over investigations into alleged Russian meddling in the 2016 USA presidential election and possible ties between his campaign and Russian officials.
The ambassador said he could not make public all details of this meeting but said the two leaders had extensively discussed some issues important to the two countries.
On Monday, Russia threatened to shoot down U.S. warplanes over Syria after a U.S. Navy fighter shot down a Syrian warplane. The U.S. was instrumental in the Western sanctions imposed on Russian Federation over its conduct.
Peter Harrell, a sanctions expert at the Center for a New American Security, said he saw the bill, which is now headed to the House of Representatives, as a sign that lawmakers were "skeptical of Trump's intentions toward Russian Federation".
Since Russia's military entry into Ukraine, the USA has put Russia under sanctions and relations between the two super powers have deteriorated.