The president of the European Council, Charles Michel, heads to Beirut on Saturday, a day ahead of a major donors conference to raise funds for the blast-damaged Lebanese capital.
"Shocked and saddened, we stand with all those affected and will provide help," Michel tweeted, announcing meetings with President Michel Aoun, parliamentary speaker Nabih Berri and Prime Minister Hassan Diab.
Michel's message was also tweeted in Arabic.
After his trip, Michel -- whose council represents the 27 EU leaders -- will take part in a videoconference organised by French President Emmanuel Macron to gather support for rescue operations.
European Commission spokesman Eric Mamer said Michel and the president of the commission, Ursula von der Leyen, had written to the 27 member states urging them to step up support for Lebanon.
At Sunday's videoconference, the EU executive will be represented by the commissioner for crisis management and humanitarian aid, Janez Lenarcic.
"We are working on an estimate of humanitarian needs and we need as much information as possible," Mamer said.
"We are in an emergency phase. This is not a conference for reconstruction. That will take place at a later stage," he warned.
The European Commission says it has coordinated the dispatch of 300 rescue experts to Beirut and has made available 33 million euros ($39 million) for initial emergency needs, including medical aid.