European Leaders to Gather in Paris to Bolster Ukraine at ‘Critical Moment’

European leaders were set to gather in Paris on Monday in an attempt to showcase unity and resolve in their support for Ukraine as the embattled country confronts a dire situation on the battlefield against Russia and in Washington, where Republicans in Congress are blocking badly needed financial aid.

The meeting, convened by President Emmanuel Macron of France, is scheduled to include about 20 or so heads of state and top officials, including from Britain, Germany, the Netherlands, Poland and Spain. President Volodymyr Zelensky of Ukraine is to attend the evening meeting by videoconference.

“We are at a critical moment,” Mr. Macron said on Saturday during a visit to a major agricultural fair in Paris, adding that the meeting would “bolster our position” and give Ukraine more “visibility” for the coming months.

“Russia cannot win in Ukraine,” he added.

A senior official in the French presidency, speaking on the condition of anonymity in keeping with French government practice, said that the meeting was not expected to end with concrete announcements of new military aid.

Instead, the official said that it was intended to shore up support for Ukraine, better coordinate aid and send a message to President Vladimir V. Putin of Russia that Europe was determined to see him fail.

There are growing worries in Europe that little has succeeded in thwarting Mr. Putin so far. Russia captured the eastern city of Avdiivka, once a Ukrainian stronghold, about a week ago in its biggest battlefield victory for months.