WELLINGTON, New Zealand — The U.S. government shutdown is threatening a long-awaited deal to create the world’s largest marine sanctuary in Antarctica. Americans are among the most enthusiastic proponents, but they might not make it to the negotiating table.

The U.S., New Zealand and other countries have sought a sanctuary in the pristine waters of the Ross Sea for the past decade, and there are hopes that previous objectors Russia and Ukraine will agree to a new, smaller proposal when the nations that regulate Antarctic fishing meet next week in Hobart, Australia.

On Wednesday, Secretary of State John Kerry joined his counterparts from other nations in calling for the sanctuary to proceed. But the U.S. had apparently already suspended travel plans for its delegation. If they don’t make it, the proposal probably will be put on hold until next year at least.

Gerry Leape, a senior international policy expert at Pew Charitable Trusts, said he’s spoken to members of the U.S. delegation and he understands that their travel has been suspended because of the shutdown.

David Edginton, a spokesman with the U.S. Embassy in Wellington, said he was unable to comment on whether the U.S. delegation will be traveling to Australia.

Leape said the suspension could be lifted on short notice, either if the shutdown ends or if the delegation gets special permission to travel. Under normal circumstances, he said, the delegation would already be in Australia and working its diplomatic channels in pre-meetings.

“It would be a real missed opportunity if the U.S. isn’t able to go,” he said. “I hope the situation changes, but they haven’t come to an agreement yet.”

Jointly proposed by the U.S. and New Zealand, the 1.34 million-square-kilometer (517,000-square-mile) sanctuary would be twice the size of Texas and the world’s largest stretch of protected ocean.

Progress on the sanctuary has already been painfully slow. The nations that make decisions about Antarctic fishing — 24 countries plus the European Union — do so only by unanimous agreement. A proposal for a larger sanctuary failed in July when Russia and the Ukraine, which have fishing interests in the region, raised objections.

The U.S. and New Zealand revised their plans, reducing the sanctuary’s proposed size by 40 percent. Environmental groups including Pew criticized the changes initially but have come to embrace the current proposal.

Next week the Antarctic nations also plan to consider a separate proposal to create a series of smaller marine reserves in East Antarctica. Those areas would come with less stringent protections than those in the Ross Sea proposal.

People involved in the negotiations say Russia remains the key to completing the Ross Sea agreement, with Ukraine likely to follow Moscow’s lead.

New Zealand Foreign Minister Murray McCully said Wednesday that Russia was ready to talk.

“I’m aware that there are some plans for dialogue with the Russian delegation, which is an encouraging sign,” he said. “We are certainly moving in a better direction than we have been previously.”

Members of the Russian delegation didn’t respond to emails from The Associated Press.

The head of the U.S. delegation, Evan Bloom, said in an interview last month that the size of the proposed sanctuary was reduced based on the findings of a committee which gives scientific advice to the nations, and that it remained faithful to the original objectives.

“One has to make tactical decisions in negotiations,” said Bloom, the director of the U.S. State Department’s Office of Ocean and Polar Affairs. “I still think the proposal is very strong, very robust, very pro-conservation, and viable.”

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