WASHINGTON, Jan. 17 -- Prior to his visit to Washington, British Prime Minister David Cameron had revealed that his relations with U.S. President Barack Obama was so cozy that the president "sometimes calls me bro."

"The president has said the special relationship is stronger than it has ever been privately and in public, and I agree," Cameron told the Daily Mail.

Given the special relationship, it therefore came as no surprise when the two leaders on Friday struck positive notes on almost every topic, from Iran and Russia to terrorism.

"We agree that the international community needs to remain united as we seek a comprehensive, diplomatic solution to prevent Iran from obtaining a nuclear weapons," said Obama at a joint press conference with Cameron. "Additional sanctions on Iran at this time would undermine that international unity and set back our chances for a diplomatic solution."

Echoing Obama, Cameron solicited space for negotiation from U.S. Congress even if he shared Obama's concern that odds of a successful deal with Iran were less than 50-50.

"It (New sanction bill) could put at risk the valuable international unity that has been so crucial to our approach," he said.

To back up his "bro," Cameron personally lobbyed Congress. "I have contacted a couple of senators this morning and I may speak to one or two more this afternoon."

U.S. Congress has prepared a new bipartisan bill on sanctions against Iran, but has yet to put it to vote as Obama has threatened to veto it.

"Congress needs to show patience," said Obama at the joint press conference. "With respect to the veto, I said to my Democratic Caucus colleagues yesterday that I will veto a bill that comes to my desk."

However, both leaders advocated strong sanctions against Russia while vowing to support Ukraine in its economic and democratic reforms.

As Obama and Cameron met in the White House one week after a wave of deadly attacks in Paris that claimed 17 lives, fears of additional attacks continued to grip the West. After Belgian police shot dead on Thursday two suspects believed to be planning an attack, raids on terrorist suspects swept across Europe.

While expressing their optimism about defeating violent extremism, both leaders admitted that intelligence and military force alone would not suffice to counter terrorism. Both said they were working together on strategies that would thwart terrorist groups' efforts to radicalize people on social media and the Internet.

"Social media and the Internet is the primary way in which these terrorist organizations are communicating," Obama said. "The laws that might have been designed for the traditional wiretap have to be updated."

British media earlier reported that during his meeting with Obama, Cameron was expected to raise the issue of U.S.-based Internet companies refusing to cooperate with British authorities during anti-terror investigations. Britain demands those U.S. companies offer access to the accounts of potential terrorists plotting attacks via social media.

In addition to fighting extremists, both governments pledged to boost cooperation in cybersecurity.

In a rather embarrassing incident, social media accounts of the U.S. military's Central Command were compromised by hackers, who claimed links with the rising terrorist group Islamic State as Obama was addressing the nation on cybersecurity.