French President François Hollande and German Chancellor Angela Merkel joined forces on Thursday in an attempt to help halt the hostilities in eastern Ukraine.

The Associated Press reported the two leaders flew to Kiev to present Ukrainian authorities with a joint peace initiative; on Friday, they plan to continue on to Moscow, where they will meet with Russian President Vladimir Putin.

"For several days, Angela Merkel and I have worked on a text ... that can be acceptable to all," Hollande said. "We will make a new proposal to solve the conflict, which will be based on Ukraine's territorial integrity."

Details on what exactly Hollande and Merkel are suggesting remain vague, and German Foreign Minister Frank-Walter Steinmeier tried to keep expectations as low as possible, Reuters noted.

"I don't want to talk about the chances (of success)," Steinmeier said. "At this stage, there is hope, rather than chances."

The security situation in eastern Ukraine, where pro-Russian separatists are battling Ukrainian forces in an increasingly violent conflict, has led to a political and economic destabilization that is of great concern to Western and Central European nations.

The United States, which has refused to recognize Putin's annexation of the Ukrainian Crimea peninsula and accuses the Russian leader of providing the militants with material support, is now considering arming the Kiev government, which could lead to further confrontation.

Russia warned any weapons shipments to Ukraine would cause "colossal damage" to its ties with the United States, Alexander Lukashevich, a foreign ministry spokesman, told Agence France-Presse.

Secretary of State John Kerry, who is said to support extending U.S. aid to Ukraine beyond the logistical assistance already provided, also visited Kiev on Thursday. Kerry said he supported the Franco-German initiative, though he was not involved in it and did not plan to accompany Hollande and Merkel to Moscow.

"We talked about the largest threat that Ukraine faces today, and that is Russia's continued aggression in the east," Kerry said after meetings with Ukrainian leaders.

A State Department official, meanwhile, revealed Kerry had promised Kiev $16 million in additional U.S. humanitarian aid.