US proposals for binding restrictions on Antarctic tourism have been adopted by countries with ties to the region, in a bid to protect the continent's fragile ecosystem, officials said Friday.

Signatories of the Antarctic Treaty, launched in Washington 50 years ago, capped 11 days of talks in Baltimore, Maryland by agreeing to impose mandatory limits on the size of cruise ships landing in Antarctica and how many passengers they can bring ashore.

Another resolution placed a mandatory shipping code on vessels in Antarctica, boosting shipping safety efforts underway at the International Maritime Organization, while a third enhanced environmental protection for the entire Antarctic ecosystem.

"We are happy with the results," said Evan Bloom, who led the US delegation at the summit, noting that the measures were largely in line with needs emphasized by US Secretary of State Hillary Clinton.

Although the measures were adopted by consensus without opposition, they were all subject to negotiation and will become legally binding once ratified by each of the 28 countries that have signed the Antarctic Treaty, he told reporters in a teleconference.

Although no specific mechanism was detailed to enforce the restrictions, signatories would be required to prevent ships with more than 500 passengers from reaching landing sites in Antarctica and allow up to 100 passengers on shore at any given time.

Nearly 400 diplomats, experts and polar scientists from 47 countries attended the meeting, which tackled environmental and territorial issues affecting the Antarctic.

The Antarctic Treaty Consultative Meeting (ATCM) also focused on promoting scientific research in the Antarctic, said its chair Tucker Scully.

He said there was "a major emphasis" on ensuring that the parties cooperated to support scientific research "to understand what is in fact happening to our planet with respect to climate."

In opening the first joint session of the ATCM and the Arctic Council on April 6, Clinton said Washington would work with other countries surrounding the region "to strengthen peace and security and support economic development and protect the environment."

The diplomatic chief said she and President Barack Obama were "committed" to having the US Congress ratify the Law of the Sea Convention, a United Nations text on maritime rights drafted in 1982.

The United States signed the convention in 1994, after securing changes to certain provisions deemed against US interests. But Congress never ratified the treaty, despite a lobbying effort by former president George W. Bush in 2007.

Clinton said Obama had provided the US Congress with an annex to the treaty for ratification. The annex set the obligations of signatories in case of an environmental catastrophe in the South Pole region.