The talks, the first between the two leaders, will take place before Trump meets Russian President Vladimir Putin, with whom he's said he'd like to improve ties.
Arriving at the West Wing on Tuesday morning, Poroshenko wasn't greeted by Trump - as the President has been known to do with other leaders - and walked into the West Wing quietly and without fanfare.
The presidency updated today's agenda last night and included the meeting between the Republican and Poroshenko, in which Pence and national security adviser, Herbert McMaster, will be also involved.
"Would the President like to see Russian Federation get out of eastern Ukraine, and does he see Moscow as the aggressor in this conflict?" They are "part of an ongoing effort to hold those responsible for violations of Ukraine's sovereignty and territorial integrity accountable for their actions", the Treasury said.
After Trump's election, both Russian Federation and Ukraine had expressed hopes that the new administration would lead to closer ties between their countries - and, given Trump's inconsistent views regarding the two countries, have both been disappointed thus far.
Romanian President Klaus Iohannis stood next to Trump for a bilateral press conference earlier this month.
USA sanctions on Russian Federation will remain in place until Moscow withdraws from eastern Ukraine, a White House spokesman said on Tuesday.
Despite the less-than-warm welcome, Trump and Poroshenko - on paper - would seem to have a lot in common. Poroshenko, a billionaire, owns Roshen, a large candy company, and 5 kanal, a Ukrainian broadcast company and Trump regularly touts his business acumen, his wealth and the fact he is new to politics.
Poroshenko said he was "confident that our effective coordination can bring peace" to his nation, which has been fighting Russia-backed separatists in eastern Ukraine since 2014.
It's still not clear what Poroshenko will get for Ukraine from the meeting with Trump. With Trump publically announcing his intention to revisit US-Russian relations upon taking office, Ukrainians have watched with bated breath.