British Prime Minister Boris Johnson and Ukrainian President Volodymyr Zelenskyy on Thursday discussed longer-term security proposals for Ukraine and ways to get grain exports out of the country, Johnson's office said.

"The leaders discussed progress in negotiations and agreed to step up work with allies, including the U.S., France and Germany, to define the longer-term security architecture for Ukraine," a spokesperson said after a telephone call between the two leaders.

"They looked at options to open up critical sea and land supply routes for Ukrainian grain stocks, and committed to direct their teams to work urgently on the next steps."