Attacks by Ukrainian long-range drones caused flight disruption at Moscow’s main airports for a third straight day on Wednesday as Russia prepared to receive the Chinese president and other foreign leaders for the annual Victory Day military parade in Red Square.

Russian flag carrier Aeroflot on Wednesday morning canceled more than 100 flights to and from Moscow. More than 140 Aeroflot flights also were delayed because of what officials described as the Ukrainian drone threat and amid heightened security measures around the Victory Day events.

Russian air defenses repelled an attack by nine drones close to the Russian capital, Moscow Mayor Sergei Sobyanin said in the early hours of Wednesday. In the evening, Sobyanin reported thwarting 15 more drones targeting Moscow, as flights were restricted in Moscow’s airports once again.

Though Ukrainian drones have targeted Moscow in the past, the sustained attacks appeared designed to disrupt preparations for the 80th anniversary celebrations marking victory over Nazi Germany in World War II — Russia’s biggest secular holiday of the year.

The repeated assaults could unnerve Russians, who have been told by President Vladimir Putin that the more than three-year war with Ukraine is going well, as well as potentially embarrass him in front of his illustrious guests.

Security is expected to be tight for Friday’s centerpiece parade. Foreign dignitaries, including China’s President Xi Jinping and Brazilian President Luiz Inácio Lula da Silva, arrived on Wednesday.

Russia plans a unilateral 72-hour ceasefire to coincide with the celebrations in Moscow. In March, the United States proposed a 30-day truce in the war, which Ukraine accepted, but the Kremlin has held out for ceasefire terms more to its liking.

Vice President JD Vance said Wednesday that the U.S. appreciated Ukraine’s willingness for a ceasefire, but the U.S. is trying to move beyond that. “What the Russians have said is ‘a 30-day ceasefire is not in our strategic interests.’ So we’ve tried to move beyond the obsession with the 30-day ceasefire and more on the, what would a long-term settlement look like?” he said.

Vance said that the next steps are to have the Russians and Ukrainians directly negotiating.

Ukrainian President Volodymyr Zelenskyy said last weekend that his country cannot provide security assurances to foreign officials planning to visit the Moscow events. Russia could stage provocations and later attempt to blame Ukraine, he said.

“Our position is very simple: we cannot take responsibility for what happens on the territory of the Russian Federation,” he said. “They are the ones providing your security, and we will not be offering any guarantees.”

Zelenskyy said that he had instructed Ukraine’s Foreign Ministry to advise foreign delegations against visiting Russia during this period.