U.S. President Donald Trump and his NATO counterparts are due to gather Tuesday for a summit that could unite the world's biggest security organization around a new defense spending pledge or widen divisions among the 32 allies.

Just a week ago, things had seemed rosy. NATO Secretary-General Mark Rutte was optimistic the European members and Canada would commit to invest at least as much of their economic growth on defense as the United States does for the first time.

Donald Trump thinks Iranians should overthrow their government if it refuses to negotiate on its nuclear program, but the US president is "still interested" in diplomacy, the White House said Monday.

"If the Iranian regime refuses to come to a peaceful diplomatic solution, which the president is still interested and engaging in, by the way, why shouldn't the Iranian people take away the power of this incredibly violent regime that has been suppressing them for decades?" Press Secretary Karoline Leavitt said on Fox News.

Several close U.S. allies urged a return to the negotiating table following American strikes on Iran that fueled fears of a wider conflict, while noting the threat posed by Tehran's nuclear program. Some countries and groups in the region, including those that support Iran, condemned the move while also urging de-escalation.

U.S. President Donald Trump described the damage as "monumental" after the U.S. hit three Iranian nuclear sites, though the U.S. assessment was unfinished.

Russian President Vladimir Putin on Monday slammed strikes on Tehran as "unprovoked aggression" and said Moscow was trying to help the Iranian people as he hosted Iranian Foreign Minister Abbas Araghchi in Moscow.

"This is an absolutely unprovoked aggression against Iran," Putin told Araghchi, calling the strikes "unjustified" and adding that Russia was "making efforts to provide assistance to the Iranian people."

Israeli strikes on Monday hit a power supply system in the Iranian capital, triggering outages in some areas around the city, Iranian media reported.

The power distribution line in northern Tehran "was damaged, causing outages in some areas", Fars news agency reported.

Ukrainian President Volodymr Zelensky landed in London on Monday and will meet with British Prime Minister Keir Starmer and other officials, a senior Ukrainian source told AFP.

"There will be plenty of meetings, with the prime minister and parliament," the source said.

The U.N. nuclear watchdog head demanded Monday the return of agency inspectors to Iran's nuclear sites in a bid to "account for" its highly enriched uranium stockpiles following attacks by Israel and the United States on its atomic program.

To be able to "return to the negotiating table", "allow IAEA inspectors, the guardians on our on behalf of the NPT to go back to Iran's nuclear sites and account for the stockpiles of uranium" including the "400 kilograms enriched to 60 percent", Rafael Grossi, director of the International Atomic Energy Agency (IAEA), told an emergency meeting of the organization's headquarters in Vienna.

The EU's top diplomat warned Monday it would be "extremely dangerous" should Iran shut down the crucial Strait of Hormuz trading route over U.S. strikes on its nuclear sites.

"Any Iranian closure of the Strait of Hormuz would be extremely dangerous," Kaja Kallas wrote on X, as EU foreign ministers met in Brussels for talks with the Iran-Israel conflict high on the agenda.

Shortly after U.S. B-2 bombers began their return to the U.S. after they struck Iran’s key nuclear facilities, U.S. President Donald Trump called Israeli Prime Minister Benjamin Netanyahu to brief him on the strike, U.S. and Israeli officials told U.S. news portal Axios.

Russia fired 352 drones and 16 missiles at Ukraine overnight, killing at least seven people in the capital Kyiv and its suburbs, Ukrainian President Volodymyr Zelensky said on Monday.

"In total, 352 drones were launched, including 159 (Iranian-designed) Shaheds just overnight, along with 16 missiles. Preliminary reports indicate that ballistic weapons from North Korea were also used," Zelensky said on social media.