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At the 77th UN General Assembly (UNGA) in New York, he said: "The international community wasn't able to hold war criminals in Syria accountable.
“What's even more disappointing is that some are trying to turn the page of the Syrian crisis, ignoring the significant sacrifices made by the blighted Syrian people.”
Syria has been engaged in a civil war since 2011. The UN's latest figures estimate that more than 306,000 civilians have been killed and almost seven million have fled the country during the 10-year period.
“The Syrian crisis has taught us a very important lesson about what can happen when the international community lacks a long-term vision in dealing with the suffering of people from ... destitution and civil wars,” Sheikh Tamim said.
“Soon enough, accompanying phenomena such as the refugee issues become the problems that we actually have to focus on.”
He commended nations that have taken in refugees from Syria but stressed the importance of addressing “the reasons for crisis before having to deal with the repercussions of crisis”.
Sheikh Tamim also warned of the failure to resolve the Palestinian issue while the “situation on the ground” changes.
“Failure to implement international resolutions and in light of the continuous change of the situation on the ground, the occupation and settlement activities will change the format of solidarity in the future,” he said.
“At this juncture, I stress that we stand in full solidarity with the brotherly Palestinian people in its aspiration to achieve justice.
“The UN Security Council must shoulder its responsibility and compel Israel to end the occupation of Palestinian territories and establish a Palestinian state on the border of 1967 with East Jerusalem as the capital.”
The Qatari leader also criticised the international community's lack of “deterring mechanisms” for “punishing those who violate sovereignty”.
Sheikh Tamim referred to the Russian invasion of Ukraine which he said contains “complexities”.
“We still call on an immediate ceasefire and peaceful settlement because this will ultimately happen regardless of how long the conflict will go on for,” he said.
“Perpetuating the crisis will not change this result, and will only increase the number of casualties and the disastrous repercussions on Europe, Russia and the global economy.”