There is "absolutely no evidence" that Russia's President Vladimir Putin wants to negotiate peace in Ukraine, the head of Britain's foreign intelligence agency said Friday in an outgoing speech.

Sir Richard Moore, chief of the Secret Intelligence Service, or MI6 as it is more commonly known, said Putin was "stringing us along."

"He seeks to impose his imperial will by all means at his disposal. But he cannot succeed," Moore said. "Bluntly, Putin has bitten off more than he can chew. He thought he was going to win an easy victory. But he — and many others — underestimated the Ukrainians."

Moore was speaking at the British consulate in Istanbul after five years as head of MI6. He leaves the post at the end of September.

During his tenure, Russia launched an invasion of Ukraine in February 2022, a war that has seen tens of thousands killed and still rages, principally in eastern Ukraine.

Moore said the invasion had strengthened Ukrainian national identity and accelerated its westward trajectory, as well as pushing Sweden and Finland to join NATO.

"Putin has sought to convince the world that Russian victory is inevitable. But he lies. He lies to the world. He lies to his people. Perhaps he even lies to himself," Moore told a news conference.

He said that Putin was "mortgaging his country's future for his own personal legacy and a distorted version of history" and the war was "accelerating this decline."

Moore, who previously served as the U.K.'s ambassador to Ankara, the Turkish capital, added that "greater powers than Russia have failed to subjugate weaker powers than Ukraine."

Analysts say Putin believes he can outlast the political commitment of Ukraine's Western partners and win a protracted war of attrition by wearing down Ukraine's smaller army with sheer weight of numbers.

Ukraine, meanwhile, is racing to expand its defense cooperation with other countries and secure billions of dollars of investment in its domestic weapons industry.

Aside from the war in Ukraine, Moore also highlighted China, Iran and counterterrorism as the agency's other priorities.

While the U.K. wants a "respectful and constructive relationship," China must stick to the "established rules of engagement and noninterference," Moore said, describing the country as one straddling "that dichotomy of opportunity and threat."

The British government has previously accused Chinese spies of targeting British officials in politics, defense and business.

Calling out Iran, North Korea and China for their support for Russia's war machine, Moore said Chinese diplomatic backing as well as the provision of "dual use" electronic components and chemicals had "prevented Putin from reaching the conclusion that peace is his best option."

A nuclear-free Iran, meanwhile, remained a priority, Moore said, warning Tehran against "blindly pursuing a strategy that destabilizes their neighborhood and puts them at odds with much of the rest of the world."

The West and Israel have long accused Iran of seeking to build nuclear weapons, a claim Iran denies. Tensions spiked during the 12-day war between Iran and Israel in June, when Israel launched airstrikes on Iranian nuclear facilities

Following the U.S. withdrawal in 2018 from the international agreement to limit Iran's nuclear program, Tehran gradually broke away from its commitments and began stepping up its nuclear activities.

The war also derailed Tehran's nuclear negotiations with the United States and prompted Iran to suspend cooperation with the International Atomic Energy Agency.

A reset in the region required a "change of mentality in Tehran, not yet detected in our intelligence," Moore said.

Such a reset also required peace in Gaza, he said, calling for an end to "further appalling suffering of innocent Palestinians."

Turning to the Islamic State group and al-Qaida, Moore said they had been damaged but were looking to reestablish themselves while using technology to "spread their violent ideologies online."

"Good partnerships" and leaders who address the root causes of radicalization are necessary to defeat efforts to terrorize, he added.

Moore is to be replaced as "C," as the head of MI6 is known, by Blaise Metreweli, who will be the service's first female chief. Moore praised her experience, especially as the agency's "Q," a position in which she has lead technological innovations in espionage.

Referring to the green ink traditionally used by MI6 chiefs, Moore said he was "now hanging up my cloak, returning my imaginary dagger to its scabbard, and handing over my famous green pen."