NEW YORK, June 29 (Reuters) - United Nations member states agreed on Tuesday to a budget of some $6 billion for the world body"s 12 peacekeeping missions for the next year, diplomats said, narrowly averting a possible shutdown of the operations. The 193-member U.N. General Assembly budget committee agreed to the peacekeeping budget for the year through June 30, 2022. It will be formally adopted by the General Assembly on Wednesday. Top U.N. officials said on Monday that U.N. peacekeeping missions - most of which are in Africa and the Middle East - had been advised to start putting contingency plans in place in case a new budget was not adopted by June 30. Some diplomats said changes to negotiating procedures, issues with logistics and tough talk pitting China against Western countries had threatened to delay an agreement. "Our chronic inability to respect deadlines puts the entire peacekeeping architecture in unprecedented jeopardy," European Union diplomat Thibault Camelli told the budget committee on Tuesday. "Going forward, and for the future negotiations, we owe it ... to the women and men in the field who carry out the peacekeeping mandates to finish our work in a timely fashion." Catherine Pollard, the U.N. head of management strategy, policy and compliance, told reporters on Monday that if the June 30 deadline was missed then Secretary-General Antonio Guterres could only spend money to safeguard U.N. assets and ensure the protection of the staff and the peacekeepers. The United States is largest assessed contributor to the peacekeeping budget, responsible for about 28%, followed by China with 15.2% and Japan with 8.5%.