Secretary of State Marco Rubio cautioned on Tuesday that the United States will cease its role as a mediator if Russia and Ukraine do not present “tangible proposals” for resolving the conflict, according to his spokesperson.

“We have reached a point where both sides must provide concrete suggestions on how to bring this conflict to a close,” State Department spokesperson Tammy Bruce informed reporters, relaying Rubio’s message.

“Should there be no advancements, we will withdraw from our mediatory role in this matter.”

She mentioned that the decision to pursue diplomatic efforts would ultimately lie with President Donald Trump.

Recently, Russian President Vladimir Putin suggested a three-day ceasefire during Moscow’s observances of the end of World War II but declined a U.S. request, supported by Ukraine, for a 30-day truce.

The United States is seeking “not a brief three-day pause for a celebration, but a comprehensive, lasting ceasefire that ends the conflict,” Bruce stated.