Leaders of NATO's 32 member countries meet this week in Washington for a summit of the transatlantic security alliance, with further military and financial support for Ukraine high on the agenda.
But much of the focus will be on U.S. President Joe Biden as some in his own Democratic Party call for him to drop his run for a second term.
The clamor follows Biden's weak performance in a debate last month against his rival in the Nov. 5 presidential election, former Republican President Donald Trump.
The outcome of the election could change the course of Washington's foreign policy.
Here are some of the leaders to watch this week at the North Atlantic Treaty Organization's meeting:
* Volodymyr Zelenskiy - In addition to drumming up more support to help repel Russia's invasion, the Ukrainian president is expected to push for a quicker path to entering NATO than the alliance has so far been willing to offer.
* Keir Starmer - The new British prime minister will make his first international trip after leading the Labour Party to a landslide victory in Britain's parliamentary election last week. Starmer has pledged to maintain the previous Conservative government's approach towards Ukraine by continuing to support Kyiv in its war against Russia's invasion.
* Emmanuel Macron - The French president will be in Washington days after losing much of his political power in a snap election. The decision to call the election stunned Macron's close allies and opponents alike, and some in his own camp denounced the move as reckless. After its second round of voting on Sunday, France faces a chaotic hung parliament.
* Viktor Orban - The Hungarian prime minister, a critic of Western military aid to Ukraine and the EU leader with the warmest relations with Russia and China, will be in Washington after a surprise visit to Beijing on Monday to discuss a potential Ukraine peace deal. Hungary assumed the six-month rotating presidency of the European Union last week, and Orban has since visited Zelenskiy and Russian President Vladimir Putin. His Russia trip angered other European leaders, who said he had no EU mandate to push for a ceasefire in Ukraine.
* Ulf Kristersson - The Swedish prime minister will represent his country at its first NATO summit since joining the alliance in March. Ahead of his trip, Kristersson said Sweden fully supports the idea that Ukraine's future lies in NATO.
* Yoon Suk Yeol - The South Korean president, who has pushed for greater security ties with Europe and other U.S. allies to deter North Korea's nuclear and missile threats, plans to discuss the threat Pyongyang poses to Europe by deepening military ties with Russia.
* Justin Trudeau - The Canadian prime minister, under pressure as his Liberal government trails the main opposition party in polls, could face renewed questions about Ottawa's defense spending lagging the 2% of gross domestic product agreed by NATO allies. In a policy update this year, the Trudeau government pledged billions more for the armed forces to increase military spending from 1.4% of GDP to 1.76% by 2030.
