US Secretary of State Rex Tillerson at the opening session of the World Conference Center Bonn | Friedemann Vogel/Pool/Getty Images Tillerson assured Ukraine of US solidarity, Poroshenko says Ukrainian leader also cautions against any deal between Washington and Moscow that does not have Kiev’s backing.

MUNICH — U.S. Secretary of State Rex Tillerson has delivered a message of solidarity to Ukraine, President Petro Poroshenko said Friday.

In a conversation on Friday afternoon, Tillerson “confirmed to me our unity … and our solidarity,” Poroshenko said during a panel discussion on Friday evening at this year’s Munich Security Conference. “This is exactly what we need now.”

Poroshenko also cautioned against any deal between U.S. President Donald Trump and Russian President Vladimir Putin that did not have the backing of Kiev.

“Any deal with Putin without Ukraine would only aggravate the situation,” he said.

During and after his winning campaign, Trump indicated he would be willing to consider easing sanctions imposed on Russia over the war in Ukraine, in exchange for cooperation in fighting terrorism. However, in recent weeks, Trump's administration has taken a harder line.

On Thursday, Tillerson told Russian Foreign Minister Sergei Lavrov that Moscow must respect its international commitments toward Ukraine.