Turkey has announced it would block two Royal Navy ships amid tensions in its waters.
Two British minehunter ships were set to transit its waters en-route to the Black Sea for use by Ukraine.
Britain said the vessels would strengthen Ukraine's sea operations in its war with Russia.
However, Turkey has announced it would block the move, saying it would violate an international pact concerning wartime passage of the straits.
Britain is looking to support Ukraine's naval strength
PA
The presidency's communications directorate informed allies that it would not allow the vessels to use its Bosphorus and Dardanelles straits as long as the war in Ukraine continues.
When the war broke out in 2022, Turkey announced it would block passage of military ships for the warring parties, citing the 1936 Montreux Convention.
The convention sets limits on the passage of civilian vessels and military warships through the Dardanelles and the Bosporus straits, linking the Aegean Sea, the Sea of Marmara and the Black Sea. The pact exempts ships returning to home bases.
The agreement was signed in 1936 by Australia, Bulgaria, France, Greece, Japan, Romania, Yugoslavia, the United Kingdom, the Soviet Union and Turkey.
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HMS Pembrooke, a Sandown-class minehunter of the Royal Navy
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A spokesperson from the presidency said that Turkey has implemented Montreux impartially and meticulously to prevent escalation in the Black Sea
Turkey maintains good ties with both Moscow and Kyiv amid the crisis.
The MoD said back in December the UK was also launching a "maritime coalition" with Norway, to garner long-term support for Ukraine.
Defence Secretary Grant Shapps also dismissed suggestions that western nations were losing interest in the war in Ukraine.
Shapps said: "We believe that we simply can't have an outcome where an autocratic dictator walks into a neighbouring democratic country and then the West gets bored of it.
"That is an unacceptable outcome. That is why the UK will keep reminding people that that can't happen."
He added that the coalition with Norway would make a "significant difference" in boosting efforts to wipe the Black Sea clean of mines.
