David Cameron Urges Parliament to Back Airstrikes Against ISIS in Iraq

LONDON - The British Parliament is to meet on Friday to vote on joining the American-led air campaign against Sunni militants of the Islamic State in Iraq.

But, wary of divisions within the political elite, government leaders have said that Britain will not join the United States in attacking targets in Syria and will not commit ground forces.

The planned British deployment is limited in scope, lagging that of France, which is already bombing targets in Iraq, and the United States, which has embarked on far more muscular strikes along with five Arab allies in Syria as well as Iraq.

Six Tornado warplanes of the Royal Air Force have been stationed at a British base on the Mediterranean island of Cyprus for several weeks, flying surveillance missions ostensibly as part of humanitarian efforts to help minorities threatened by the advance of fighters from the Islamic State, who spilled into Iraq from Syria in June.

The airplanes could be flying combat missions within days, officials have said.

Prime Minister David Cameron has approached the vote cautiously since, in a politically embarrassing ballot last year, Parliament refused by a narrow margin to endorse military action in Syria in support of the United States following the use of chemical weapons in the civil war there. This time, senior officials argue that Britain has been invited by the new government in Baghdad to come to its defense, offering a legal basis for intervention.

At the same time, the assurance that Britain's deployment will be limited to Iraq and exclude ground forces was designed in part to ensure the support of the opposition Labour Party, whose leader, Ed Miliband, has expressed concern about attacks in Syria without the approval of the United Nations.

Even so, some lawmakers from the Labour Party have misgivings about supporting the deployment, Diane Abbott, a member of the party, said in a radio interview on Friday.

The debate was due to start at 10:30 a.m. and a vote was expected around 5 p.m.

The situation is particularly tangled because militants of the Islamic State, which is also known as the Islamic State in Iraq and Syria, or ISIS, are holding Western hostages including a British taxi driver, Alan Henning, whom they have threatened to execute.

Additionally, British news reports said a small number of the British Muslims who have joined ISIS forces were killed in earlier American airstrikes. The presence of Western militants in the ranks of ISIS has fueled concern that some of them may return to their home countries to launch retaliatory attacks.

Gilles de Kerchove, the European Union's counterterrorism chief, was quoted by the BBC on Friday as saying the total number of Europeans fighting with the militants in Syria and Iraq now stood at 3,000. He also warned that Western airstrikes would increase the risk of retaliatory attacks.

On Thursday, the British cabinet unanimously backed joining the United States and France in attacking militant targets in Iraq. But the government said it would not seek to extend its deployment to Syria without a further vote in Parliament.

The British defense secretary, Michael Fallon, quoted Secretary of State John Kerry as estimating that the campaign could last two to three years. 'That looks like a long haul to me,' Mr. Fallon said.

Even as Britain prepared to join the United States in the airstrikes, relations between the two countries' security services grew strained after the director of the Federal Bureau of Investigation, James B. Comey, said an ISIS figure seen beheading two American journalists and a British aid worker in jihadi videos had been identified.

While Mr. Comey did not provide a name, British security officials were widely quoted as expressing frustration that the disclosure could jeopardize investigations by counterterrorism officials.