Obama, Cameron pledge a joint security effort
Cameron's visit to Washington came one week after 17 people were killed in attacks in France, heightening fears in Europe and the United States about the spread of terrorism.
"This is a problem that causes great heartache and tragedy and destruction," Obama said in a joint news conference with Cameron. "But it is one that ultimately we are going to defeat."
The prime minister was blistering in his assessment of those responsible for the attacks, calling them part of a "poisonous, fanatical, death cult."
"We know what we're up against, and we know how we will win," Cameron said. He spoke as British police chiefs announced that the Paris attack on a kosher supermarket and anti-Semitic rhetoric from extremists had led them to study ways to increase protection for the Jewish community.
As Obama and Cameron met at the White House, representatives from their countries were joining negotiating partners for another round of nuclear talks with Iran. Both leaders strenuously urged Congress to avoid ordering new economic sanctions on Iran in the midst of those negotiations, arguing that doing so could upend the delicate diplomacy.
"Why is it that we would have to take actions that might jeopardize the possibility of getting a deal over the next 60 or 90 days?" asked Obama, who said he would veto legislation if it reached his desk. "What is it precisely that's going to be accomplished?"
Negotiators have set a March deadline for reaching a framework that would address the international concerns about Iran's nuclear program.
Cameron said he had called some senators Friday to make the case for holding off on new penalties.
The prime minister arrived in Washington with a request for Obama to help persuade U.S. technology companies to give governments more access to encrypted communications that terrorists may use to plot attacks. Cameron's policy proposals have stoked concern on both sides of the Atlantic about the prospect of security efforts encroaching on privacy, particularly in the aftermath of the 2013 spying disclosures by former NSA contractor Edward Snowden.
