A former diplomat advises Biden to demonstrate his relevance at the NATO summit.

• The NATO alliance's 75th anniversary summit is taking place in Washington this week, with high stakes at play.
• Amidst concerns about his age and mental fitness for the presidency, U.S. President Joe Biden faces scrutiny.
• The organization's primary objective is currently to aid Ukraine in its conflict with Russia, but there is concern among members that this support may be at risk if Donald Trump is elected as the US president in November.

The NATO alliance's 75th anniversary summit is taking place in Washington this week, with high stakes at play.

Amid concerns about his age and mental fitness for the presidency, U.S. President Joe Biden faced criticism following his poor debate performance against former President Donald Trump in June.

In a discussion with CNBC's Capital Connection on Tuesday, Rose Gottemoeller, the former NATO deputy secretary-general, emphasized this point.

"The upcoming NATO summit in Washington is crucial for Joe Biden to demonstrate his leadership abilities and commitment to the alliance, as he continues to lead not only the United States but also NATO, according to a CNBC interview with Dan Murphy."

According to Gottemoeller, the summit is crucial for the NATO alliance, but not a make-or-break. NATO has faced challenges in the past and has weathered crises, making it a resilient alliance.

The organization's primary concern is currently aiding Ukraine in its conflict with Russia, which some members worry could be jeopardized if Trump is elected president of the United States in November.

The lion's share of financial and military support to Kyiv comes from the U.S., and Trump has threatened to withdraw the U.S. from the alliance if he is reelected and continues to oppose sending military aid to Ukraine.

"According to Gottemoeller, there will be significant pressure on the alliance from Donald Trump, as there was during his first term when he served as deputy secretary-general at NATO. Trump was relentless in pushing NATO allies to increase their defense spending."

Trump frequently warned NATO members who did not meet the alliance's spending requirement of 2% or more of their national budget on defense that he would allow Russian President Putin to attack them. During a February campaign rally, he stated that he would permit Putin to attack countries that did not allocate sufficient funds to their defense.

If Trump wins a second term, he will see a much different NATO, according to Gottemoeller. She said that he played a crucial role in getting NATO to spend more on its own defense, but emphasized that member states have been taking significant steps in response to Putin's full-scale invasion of Ukraine.

According to Gottemoeller, the number of NATO member states spending 2% or more of their GDP on defense has increased from fewer than 10 to 23 out of the alliance's 32 current members while Trump was in office.

Despite Trump's threats on the campaign trail to withdraw from NATO, Gottemoeller, who teaches at Stanford University, expressed skepticism that he would actually follow through with it. However, if Trump were to win, it would be "very, very important for NATO allies to pay close attention to him and what he wants to accomplish," said the former diplomat.

During his second term, Trump will likely demand that NATO allies increase their spending beyond 2%, as he has done before.

From 2016 to 2019, Gottemoeller served as NATO's deputy secretary-general and, in the early 1990s, as director for Russia, Ukraine and Eurasia affairs on the National Security Council. She later held the position of under-secretary of state for Arms Control and International Security at the State Department.