Despite warnings from the Kremlin against joining NATO, Ukrainian President Petro Poroshenko was at the opening of an important summit for the 28-nation alliance being held in Wales.

Before the NATO nations began formal meetings, Poroshenko had already met with leaders from the U.S., the U.K., France, Germany and Italy, looking for support from the West in Ukraine's conflict with Russia, according to USA Today.

This bold move by Poroshenko could hinder relations with Russia that are already close to a breaking point after five months of conflict between Ukraine and pro-Russian rebels in eastern Ukraine. Russia has voiced clear warnings against Ukraine joining NATO.

Russian Foreign Minister Sergei Lavrov said agreements reached with NATO against Russia could endanger the shaky peace agreed between the two countries, The Washington Post reported. He also warned the U.S. not to impose its will on Ukraine.

Russia has been criticized by NATO for sending weapons and troops to help the rebels in eastern Ukraine, though the Kremlin denies these allegations. More than 2,600 people have died since the conflict started in April.

"We meet at a time when the world faces many dangerous and evolving challenges," U.S. President Obama and U.K. Prime Minister David Cameron wrote in a joint op-ed for The Times of London. "To the east, Russia has ripped up the rulebook with its illegal, self-declared annexation of Crimea and its troops on Ukrainian soil threatening a sovereign nation."

Both Poroshenko and the leaders of the pro-Russian rebels have a tentative ceasefire agreement, which goes into effect at 2 p.m. local time on Friday, pending final approval on both sides. It's not clear how Poroshenko's presence at the NATO summit will affect the ceasefire.

NATO leaders have told Poroshenko that NATO membership for Ukraine won't happen anytime soon, but member nations are expected to express support for Ukraine in its conflict with the rebels.