An effective global response is needed to protect the UK's values from terrorism and other threats, Home Secretary Theresa May said today.
Mrs May highlighted the importance of cooperation with the United States over security issues after meeting her US counterpart Janet Napolitano for private talks in London.
It comes after Scotland Yard said a bomb found on a cargo plane at East Midlands Airport in October was timed to detonate over the eastern seaboard of the US.
The pair talked about a range of issues, including cyber, cargo and aviation security, officials said.
Mrs May also outlined plans for the future of the UK's counter-terrorism powers, which were published earlier this week.
They include replacing controversial control orders for suspected terrorists who cannot be prosecuted with terrorism prevention and investigation measures, Tpims, which have been dubbed "control orders-lite" by critics.
Other proposals include ending the indiscriminate use of terrorism stop-and-search powers, banning councils from using surveillance powers to investigate low-level offences and launching a stronger effort to deport foreign nationals involved in terrorist activity.
This week also saw the end of 28-day detention without charge, which was allowed to lapse back to 14 hours on Tuesday.
Mrs May said: "The UK-US relationship is incredibly important to both our countries and I was delighted to meet with Secretary Napolitano this afternoon to reaffirm our shared purpose, in particular around tackling the security issues we face.
"We agreed that global threats require an effective global response.
"Only by working together, and in close cooperation with our international partners, can we protect the freedoms and values we share."
Ms Napolitano, the US Homeland Security Secretary, announced yesterday that the current colour-coded terror threats to the US, which rate the threat as shades of green, blue, yellow, orange and red, will stop being issued from April.
Instead, a new National Terrorism Advisory System (Ntas) will provided timely and detailed information on specific threats.
"Security is a shared responsibility, and we must work together to keep our nation safe from threats," Ms Napolitano said.
"This new system is built on a clear and simple premise: when a credible threat develops that could impact the public, we will tell you and provide whatever information we can so that you know how to keep yourselves, your families and your communities safe.
"These alerts will include a clear statement that there is an 'imminent threat' or 'elevated threat'.
"The alerts also will provide a concise summary of the potential threat, information about actions being taken to ensure public safety, and recommended steps that individuals and communities can take.
"The new system reflects the reality that we must always be on alert and be ready."
Speaking at George Washington University in the US capital, Ms Napolitano added that the alerts may be limited to a particular audience - such as police or shopping centres of hotels - or may be issued more broadly to the public.
Last year, police said the bomb discovered at East Midlands Airport was disguised as an ink cartridge on a UPS aircraft.
Leicestershire police officers found the device shortly after 3.30am on October 29 last year and it was timed to go off some seven hours later over the eastern seaboard of the US, Scotland Yard said.
It was one of two bombs thought to have been made and dispatched by al Qaida in the Arabian Peninsula (Aqap).
As part of new security measures brought in following the foiled attacks, countries sending air freight to the UK are being "graded" according to risk and rules which allowed some freight not to be rescreened if it was merely passing through the UK were amended.
The FBI and Homeland Security Department in the US warned local officials across the country that packages from abroad with no return address and excessive postage required a second examination.
In the UK, the Government's national security strategy also highlighted attacks on computer networks as one of the country's biggest emerging threats.