LONDON (AP) — Secretary of State John Kerry issued a warning Monday to Islamic State militants that "we are not intimidated" after another American hostage was killed.
Kerry said the brutality of the Islamic State group and its potential spread worldwide was a key reason, among many, that the United States must remain deeply engaged in the Mideast.
His comments came right before he headed overseas for nuclear talks with Iran as a November 24 deadline for a deal looms.
"We are obviously entering in a key period with negotiations regarding Iran's nuclear program," Kerry said at an annual policy forum in Washington, hosted by the publisher of Foreign Policy magazine.
But the bulk of his comments sought to underline the case for deep U.S. involvement in the Mideast. "We have to be deeply engaged — deeply engaged — in this region, because it is directly in the interest of our national security and our economy, and it is also in keeping of who we are," Kerry said.
He added: "The United States does not go in search of enemies in the Middle East. There are times, however, and this is one, when enemies come in search of us."
A day earlier, the White House confirmed the death of U.S. aid worker Peter Kassig, a former soldier who tried to help wounded Syrians caught in their country's civil war but ended up dying himself at the hands of Islamic State. The militant group that controls much of northern Syria and Iraq has now killed five Westerners it was holding.
The IS video of a militant boasting about killing Kassig also appears to show extremists beheading a dozen Syrian soldiers. Kassig was captured by the extremists in eastern Syria on Oct. 1, 2013, while delivering relief supplies for the aid group he founded.
Left unchecked, Kerry said that the Islamic State group could grow worldwide. Already, he said, the IS has seized more land and resources "than al-Qaida ever had on its best day of its existence."
IS "leaders assume that the world will be too intimidated to oppose them," Kerry said. "But let us be clear: We are not intimidated."
Immediately after the speech, Kerry headed to London, where he will hold talks with European and Mideast officials on volatile situations in the Mideast, as well as on the Iran negotiations, which are set to expire next week. Kerry also plans to meet with the Egyptian and Emirati foreign ministers as well as the foreign minister of Oman.
Oman appears to have emerged as a key player in the Iran talks outside the formal negotiating group of the U.S., Britain, China, France, Russia and the European Union, known as the P5+1.
Oman, which has close ties with Iran, was the site of secret talks between American and Iranian diplomats in March 2013 and hosted the last round of high-level talks earlier this month in Muscat. On the heels of those talks, Oman's foreign minister paid a visit to Tehran over the weekend, according to Iranian media reports.
From London, Kerry will travel to Vienna, where the next round of nuclear talks is set to begin on Tuesday and continue through the week, the State Department says.
World powers have for years sought to strike a deal with Tehran to limit its nuclear program to a point where it cannot produce an atomic weapon. In return, the West would ease sanctions on Iran's oil and financial sectors that have crippled the Islamic Republic's economy.
Such an agreement would mark an unprecedented victory after a generation of mutual distrust and between Iran and much of the rest of the world. But a senior State Department official on Monday voiced skepticism about a final deal, and said there are no plans to extend the talks past the Nov. 24 deadline.
"We still have gaps to close, and we do not yet know if we will be able to do so," said the official who was not authorized to brief reporters by name and spoke on condition of anonymity.
Kerry may not take part in all the negotiating sessions in Vienna, and other stops are possible, officials said Monday.