Ukrainian President Petro Poroshenko said he was contented with the results of his negotiations with U.S. President Donald Trump and Vice President Mike Pence at the White House on Tuesday.

"Grateful to our partners for the support of Ukraine. Our meetings in the WH got very wide agenda. I am delighted with the results of the negotiations with @realDonaldTrump and @VP," Poroshenko wrote on his Twitter account.

Ukrainian Ambassador to the U.S. Valeriy Chaly said the meeting between the two presidents lasted for half an hour and was very constructive.

Poroshenko also planned to meet with U.S. Secretary of State Rex Tillerson and visit the Pentagon later on Tuesday.

First Deputy Chairperson of the Ukrainian Verkhovna Rada Iryna Gerashchenko said Poroshenko and the Ukrainian delegation were scheduled to meet on Tuesday with the U.S. secretary of state, defense secretary, the IMF and World Bank management, senators, and other influential U.S. politicians.

It was important that the conversation between Poroshenko and Trump took place before a G20 summit, as "Donbas and Crimea will be among its subjects," Gerashchenko wrote on Facebook.

"At the meeting between the presidents of Ukraine and the U.S., Poroshenko and Trump discussed bilateral relations between the countries, economic cooperation, support for Ukrainian reforms, and, surely, the security situation in Donbas and the occupation of Crimea," Gerashchenko said. "This was a full-format and productive meeting," she said.

Security in Donbas and military-technical cooperation were the key subjects of Poroshenko's meeting with Pence, she said.

"They also attached particular significance to the issue of hostages, which is a priority for Ukraine. I'd like to emphasize that President Poroshenko handed a letter from relatives of the hostages and political prisoners held in the occupied Donbas and in Russia to Vice President Pence. We are appealing to the whole world with this request: help free the guys, we believe the U.S. administration will be actively cooperating with us on this issue," Gerashchenko said.