Amid a backlash over Turkey's domestic repression, President Recep Tayyip Erdogan used a visit to London to lambast Donald Trump on Monday, saying the United States had lost its mediating role in the region.
Mr Erdogan's comments came as dozens of Palestinians were killed by Israeli security forces at border in Gaza. The Turkish leader used a speech at the Chatham House think tank to attack the US president and his decision to move its embassy from Tel Aviv to the disputed city of Jerusalem.
During his three-day trip to Britain, Mr Erdogan will meet Queen Elizabeth II and hold working meetings with Prime Minister Theresa May.
But he focused on US involvement in the Middle East, describing the embassy move as "very, very unfortunate", also criticising Mr Trump’s withdrawal from the Iran nuclear deal, an agreement Mr Erdogan said "should be preserved".
"With its latest step America has chosen to be a part of the problem, not a solution, and lost its mediator role in the Middle East peace process," he said, condemning the relocation of the US embassy from Tel Aviv to Jerusalem as it would "increase tensions and ignite an even greater fire between communities".
"The international community must do its part as soon as possible and take swift action to put an end to Israel's increasing aggression," he said.
"The establishment of an independent Palestinian state with Jerusalem as its capital is the only way for lasting peace and stability."
Mr Erdogan also outlined wider concerns about the Middle East, quoting Shakespeare's Hamlet in his opening line: "The times are out of joint."
On the Iran deal, Mr Erdogan said the region benefited from Iran's "contributions to stability", adding that positive relations with Tehran would also help to ensure a stable, prosperous Iraq.
Mr Erdogan's attack on Mr Trump's policies was expected, according to analysts from the Royal United Services Institute.
"Erdogan already led the criticism of the embassy move," said Jonathan Eyal, RUSI international director. "It has become for him a badge of honour to bait and criticise the Americans at every stage ... At the same time, he seems to offer no workable alternatives. I fail to see what is his workable alternative to the Iranian involvement in Syria, or their meddling in other parts of the Middle East."
"The region does not benefit from Iran's 'contribution to stability'," he added. "Iran is not part of the solution, it is part of the problem."
Touching on Turkey’s own domestic affairs, Mr Erdogan insisted the country had not stepped back from laws and freedom. The topic was controversial, however, with loud protests taking place outside Chatham House as he spoke.
British opposition MPs such as Labour's David Lammy also added their voice to the criticism, accusing Prime Minister May of "rolling out the red carpet" for Mr Erdogan, despite his questionable track record on civil liberties. "He is a dictator and tyrant who locks up journalists, has installed a regime of brutal repression and torture and is butchering the Kurds," Mr Lammy wrote on Twitter.
Mr Erdogan promised not to stay in power “eternally”, as the country prepares for snap parliamentary and presidential elections on June 24. The early election is set to accelerate Turkey's transition to the new presidential system with full executive powers, but critics fear it will lead to one-man rule.
"We are determined to continue with our reforms after being granted approval by our people on June 24th," he said.
He also used his speech to touch on the plight of Syrians, the spread of terrorist organisations and the surge of tensions in Palestine, adding that the international community had so far failed to address these issues.
He called for more responsibility and accountability from all countries on the UN Security Council, saying that world was “more than just five members”.
In a sign of the heated tensions around Mr Erdogan's visit to Britain, his meeting with a number of Turkish football stars on Monday also sparked debate on social media. People speculated whether the players, such as Mesut Ozil and Ilkay Gundogan who play for Germany, will now be kicked out by Germany because they met a "dictator", as the country's media frequently claims.
On Sunday, Mr Erdogan opened his visit by praising the country as "an ally and a strategic partner, but also a real friend”.
Speaking at a forum on Turkish-British relations, Mr Erdogan said bilateral co-operation between the two countries had grown in recent years.
The deepening ties are most evident in trade, he said, with a joint goal of increasing trade volume from $16 billion (Dh59) to $20 billion and a potential free trade agreement in the works. He cited British-Turkish co-operation in defence industries as an example for more new ventures.
Topics to be discussed with Mrs May include the latest developments in Cyprus, where Turkey and Britain both act as guarantors, and a "joint action plan" for the Middle East, especially Syria, Iraq and Iran.