London: Britain may join the United States "shoulder to shoulder" in operations against Islamic State militants in Iraq and Syria, a US general and presidential envoy said on Wednesday.
John Allen, who is coordinating the US-led campaign against the jihadist group, spoke after meeting the British foreign secretary.
Asked about an alliance between the US and Britain, Allen told the BBC programme Newsnight "we were shoulder to shoulder in Iraq, we were shoulder to shoulder in Afghanistan".
"We are in close consultation now as the strategy begins to unfold with respect to dealing with ISIL, and I suspect we`ll be able to say shortly that we`re shoulder to shoulder here as well," Allen said, using another name for IS.
Asked whether this meant that Britain would be involved in Syria as well as Iraq, Allen said "Well they will support us I think in the strategy... that`s a conversation we`re having right now."
London was the first stop in a series of meetings in Europe and the Middle East as the general seeks to rally opposition to the jihadist group.
IS has declared an Islamic "caliphate" in the large areas it controls in Iraq and Syria, and has killed hundreds of people and beheaded a series of foreign hostages.
British jets are part of an international alliance bombing IS in Iraq, but the country has so far been resistant to getting involved in Syria -- a web of feuding groups after years of civil war.
Allen said that training of opposition groups on the ground would continue, as in the Syrian town of Kobane where a fight between IS and Kurdish fighters backed by airstrikes has become a key battleground.
However, Allen said that physical force was not enough to tackle the problem.
"It`s not enough to defeat ISIL in a physical manner, we have to defeat the idea of ISIL," Allen said. "We all need to come together to deal with the underlying causes that generate extremism."
British Foreign Secretary Philip Hammond said after meeting Allen that "tackling the threat posed by ISIL demands a long-term, comprehensive and coordinated international response."
"In both Iraq and Syria, people want stable, inclusive, non-sectarian governments that can provide prosperity and security, but instead they find themselves on the front line in resisting terrorists and extremists," Hammond said in a statement.
"The UK and its allies will continue to support them and to play a strong and active part in the international coalition that is degrading ISIL."
"Both our national security and the security of the region depend on tackling this scourge."
The US has repeatedly emphasised the importance of regional allies in the fight against IS, and Allen will next travel to France for meetings, followed by a trip to several gulf states who have backed airstrikes including Saudi Arabia, Bahrain, Qatar and United Arab Emirates.