(Bloomberg) -- Turkey is preparing to host the third international gathering of national security advisers working to build support for a peace summit Ukraine wants to hold later this year, according to people familiar with the matter.

The meeting is tentatively scheduled for later this month in Istanbul, according to the people who spoke on condition of anonymity to share information about the plans for the summit. It follows similar gatherings in Denmark in June and in Saudi Arabia in August. Participants will discuss ideas for reaching a lasting peace in Ukraine.

A limited number of officials are expected to participate in the meeting, including US officials, if the meeting comes together, two of the people said. The White House hasn’t determined exactly who will participate. 

Russia is not invited and has denounced the previous meetings as illegitimate. 

White House spokespeople declined to comment.

Ukrainian and allied officials have sought to persuade countries that have stayed mostly neutral toward Russia’s invasion, such as Brazil and India, to side against Moscow. Allies see the meetings as an opportunity for Ukraine to explain its case directly with those nations.

On the agenda is Volodymyr Zelenskiy’s peace plan and the Ukrainian president’s efforts to hold a global summit on the proposals later this year. Zelenskiy’s 10-point blueprint calls for Russian troops to withdraw completely from Ukraine, and also covers topics such as ensuring food security and nuclear safety.

The gathering comes as Ukraine’s counteroffensive has been making slow progress against Russian forces. At the same time, concerns about political support in the US for continued aid have surged after the funding was left out of a stopgap budget plan passed over the weekend.

Bickering among US House Republicans over whether Ukraine assistance should be included in that package helped lead to the historic ouster of Speaker Kevin McCarthy. His successor could face even more pressure from ultra-conservative GOP lawmakers to block additional funds for Kyiv.

In August, the Saudi government invited national security and diplomatic advisers from Ukraine, several of Kyiv’s key allies and others in the Group of 20 such as India, Brazil and China, for talks. Representatives from about 40 countries attended, including Sullivan and China’s special envoy for Eurasian affairs, Li Hui.

Allies are eager for China to attend the next round of discussions but it is unclear if Beijing will send a representative, according to the people familiar with the plans.

South Africa was floated as a possible location for the next round of talks, but leaders there declined due to logistical considerations after recently hosting the BRICS summit. The country is also preparing for the African Growth and Opportunity Act summit in Johannesburg in November.

--With assistance from Alberto Nardelli.

(Updates with details on meeting, in third paragraph.)

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