LONDON, ENGLAND -- President Obama's spending his third day in Europe holding a bilateral meeting and press conference with British Prime Minister David Cameron and giving remarks to Parliament, which aides described as the "anchor" of his trip.

Cameron and Obama described in an op-ed in Tuesday's Times of London not just a special relationship, but an "essential relationship" when it comes to issues of global security.

Obama will be the third U.S. president to make such an address - former Presidents Bill Clinton and Ronald Reagan also gave speeches to the British lawmakers.

The president is expected to discuss the deep U.S and U.K ties and joint push for democracy as seen in the sweeping protests in the Middle East in countries like Egypt and Tunisia. The parliament speech is anticipated to echo those themes.

"The United States and the United Kingdom, along with our allies, are the ones who shoulder particular burdens for global security," said Deputy National Security Advisor Ben Rhodes at a briefing Tuesday. He underscored the war in Afghanistan, mission in Libya and sanctions on Iran and North Korea as examples.

The president's meeting with Cameron is expected to touch on a host of issues and weigh heavily on foreign policy. Cameron is reportedly looking for the U.S. to step up a more aggressive role in Libya, where Muammar Qaddafi is fighting to remain in power as NATO is taking over command. Administration officials said they weren't looking to escalate the U.S. presence and the White House is wrangling with U.S. lawmakers over Congressional approval on any action in Libya.

The war in Afghanistan will also be high on the agenda. Cameron is withdrawing 400 of the 10,000 troops in Afghanistan and the U.S. is preparing for a July deadline which would also draw down some U.S. troops. Besides national security issues, the two will also likely discuss the economy.

Obama spent Monday in Ireland giving remarks in Dublin and visiting the small town of Moneygall where genealogists say he has ancestral ties. Tuesday he had an official state visit and dinner with Queen Elizabeth full of royal pageantry and grand diplomatic gestures. Obama heads to Deauville, France Thursday for the G-8 summit and then wraps up his European swing in Warsaw, Poland.