- Summary- Companies- Russia rejoins Black Sea grain corridor pact in U-turn- Had pulled out after alleged Ukraine attack on its fleet- Says it has now received guarantees from Ukraine- Announced guarantees go no further than original deal- Deal vital to easing world food crisisANKARA/KYIV, Nov 2 (Reuters) - Russia said on Wednesday it would resume its participation in a deal freeing up grain exports from war-torn Ukraine, reversing a move that world leaders had said threatened to exacerbate global hunger.Andrey Sizov, head of Russia-focused Sovecon agriculture consultancy, said Moscow's decision was "quite an unexpected turnaround" but the deal remained shaky given uncertainty about whether it would be extended past its Nov. 19 expiry.FOOD SHORTAGESThe Russian blockade of Ukrainian exports through the Black Sea since its invasion of Ukraine on Feb. 24 has worsened food shortages and a cost of living crisis in many countries.The grains deal aimed to help avert famine in poorer countries by injecting more wheat, sunflower oil and fertilizer into world markets.Turkish Foreign Minister Mevlu Cavusoglu said earlier Russia was concerned about its fertilizer and grain exports, echoing Russian officials in saying ships carrying them could not dock even though the exports were not included in Western sanctions."