The Kremlin said on Thursday there were still "a lot of questions" remaining over the Black Sea grain deal, and that there were currently no plans for talks between President Vladimir Putin and UN Secretary-General Antonio Guterres, reported Reuters.

The Black Sea Grain Initiative, brokered by the United Nations and Turkey last July, aimed to prevent a global food crisis by allowing grain blockaded by Russia's invasion to be safely exported from three Ukrainian ports.

The deal was extended for 120 days in November and is up for renewal again on March 18. However it cannot be renewed if Russia objects and Moscow has already signalled that it is unhappy with how the deal is being implemented.

"There are still a lot of questions about the final recipients, questions about where most of the grain is going. And of course, questions about the second part of the agreements are well known to all," Kremlin spokesman Dmitry Peskov said.

Russia has complained before that most of the Ukrainian grain exported under the deal is going to wealthy countries. The "second part" of the deal refers to a memorandum of understanding with the United Nations which facilitates Russian food and fertiliser exports.

Russia's agricultural exports have not been explicitly targeted by Western sanctions, but Moscow says restrictions on its payments, logistics and insurance industries are a "barrier" to it being able to export its own grains and fertilisers.

UN chief Guterres met Ukrainian President Volodymyr Zelenskiy in Kyiv on Wednesday to discuss extending the deal, while a top UN trade official is due to meet senior Russian officials in Geneva next week.

Ukraine has so far exported more than 23 million tonnes of mainly corn and wheat under the deal, according to the United Nations. The top primary destinations for shipments have been China, Spain, Turkey, Italy and the Netherlands.