Advances in the campaign against the Islamic State in Syria and Iraq are forcing the extremists to abandon territory there, generating concerns that they are carving out a new stronghold in oil-rich Libya, Secretary of State John F. Kerry said Tuesday.

“As everybody here knows, that country has resources,” Kerry said at a conference of 23 foreign ministers from nations that form the core of a coalition fighting the Islamic State. “The last thing in the world you’d want is a false caliphate with access to billions of dollars in oil revenue.”

Both Kerry and Italian Foreign Minister Paolo Gentiloni said the radical Islamist group is expanding its presence in Libya, as fighters pushed out of Iraq and Syria relocate there and are joined by others new to the battle.

In a joint statement, the foreign ministers expressed concern over the “growing influence” of the Islamic State in Libya. They vowed to “continue to monitor closely developments there, and stand ready to support the Government of National Accord in its efforts to establish peace and security for the Libyan people.”

Kerry ruled out military intervention in Libya by the United States in the near future. But he said that could change if there were “some turn of events, like weapons of mass destruction ending up in the hands of the wrong people.”

Libya has been in a state of chaos since 2011 when longtime dictator Moammar Gaddafi was ousted. Two rival governments subsequently emerged, and continuing conflict has foiled efforts to establish a united Libyan government.

Though the emerging threat in Libya commanded much of the diplomats’ attention, the situation in Syria remains troublesome. Success in pushing Islamic State fighters out of an estimated 40 percent of territory they controlled in Iraq and 20 percent to 30 percent of the land they held in Syria has created its own set of urgent problems.

[U.S. envoy slips into Syria to encourage anti-ISIS forces]

Fleeing fighters often booby-trap homes and demolish buildings, which then need to be cleared and rebuilt before residents can return. Kerry urged his fellow foreign ministers to donate more money to a stabilization fund for rebuilding and restoring services in those areas.

Now that U.N.-backed Syria peace talks aimed at ending the war have started in Geneva, Kerry called on Russia to stop bombing opposition fighters and the Syrian government to grant humanitarian access to besieged towns.

“We are at the table, and we expect a cease-fire,” he said. “And we expect adherence to the cease-fire, and we expect full humanitarian access.”

In Geneva, where U.N. envoy Staffan de Mistura on Monday declared the official opening of talks between the Syrian government and opposition, both sides said that as far as they were concerned, negotiations had not yet begun.

In a statement, the opposition delegation said Syrian rebels are facing “a massive acceleration of Russian and regime military aggression . . . including attacks on hospitals and critical infrastructure” near the cities of Aleppo and Homs over the past two days. It repeated the opposition’s insistence that formal negotiations cannot start until the attacks cease.

The Syrian government delegation accused the opposition of acting like “amateurs and not professional politicians.” Syria’s United Nations ambassador, Bashar Jaafari, representing Syrian President Bashar al-Assad, said his side challenged the participation of two “terrorist” groups in the opposition delegation, according to the state-run Syrian Arab News Agency.

The Obama administration is eager for the peace talks to begin and has pressured the opposition to participate. Opposition representatives have said the agreed-upon rules for the negotiations, in a U.N. resolution, call for an end to bombardments and government sieges of civilian areas, as well as the release of prisoners.

Russian Foreign Minister Sergei Lavrov, on a visit to the United Arab Emirates, told reporters there that his government considered members of Jaish al-Islam and Ahrar al-Sham to be participating in the opposition delegation in their “personal capacity” rather than as official representatives. Russia and Syria consider the groups, which control thousands of opposition fighters in Syria, to be “terrorist” organizations, and Syria has objected to their inclusion.

Lavrov also said that he considers it the responsibility of the United States, as leader of the coalition against the Islamic State in Syria and Iraq, to prevent conflict among the various participants operating strike aircraft over those countries.

Karen DeYoung in Washington contributed to this report.

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