The House on Monday passed a resolution urging the president to provide Ukraine with military assistance amid its conflict with Russia.
Passed by a 348-48 tally, the measure calls on President Obama to give Ukraine lethal weapons, instead of only humanitarian support.
"We are at a turning point," Royce said. "If we allow aggression against Ukraine to stand without us at least offering the Ukrainians the ability to defend themselves, we will signal to the world that our willingness to defend the post-World War II order is crumbling."
During his address to Congress in September, Ukrainian President Petro Poroshenko asked Congress to authorize providing more military equipment in the fight against pro-Russia separatists.
The Obama administration has issued sanctions against Russia and delivered non-lethal military aid to Ukraine, including medical kits and blankets.
"They need more military equipment, both lethal and non-lethal," Poroshenko implored Congress of his government's troops. "One cannot win a war with blankets."
Lawmakers argued that Ukraine has been unable to match the advanced equipment Russia is using, thereby requiring help from the U.S. Rep. Eliot Engel (D-N.Y.), the top Democrat on the House Foreign Affairs Committee, stressed that it wouldn't amount to the U.S. entering a new war.
"The people of Ukraine are not looking for American troops," Engel said. "They are just looking for the weapons to defend themselves. They don't have those weapons. We do."
"If we don't act now, who will?" Engel asked.
Congress unanimously cleared a bill last year authorizing the president to provide military assistance to Ukraine and impose additional sanctions against Russia. However, the obama administration has yet to send Ukraine military help.
Updated at 8:01 p.m.