Iran's nuclear programme, which Erdogan has defended much to the dismay of Turkey's Western allies, is also likely to be high on the agenda.

Erdogan, whose country is a key Muslim ally of the US, visits Washington after Obama announced that 30,000 more soldiers would be sent to Afghanistan and US allies followed suit Friday by pledging at least 7,000 more troops to help defeat the Taliban and al-Qaeda.

Even though it has NATO's second largest standing army, Turkey insists it will not engage in combat missions and offered only three teams to train Afghan security personnel, according to NATO sources.

Some 1,700 Turkish soldiers are currently deployed in Afghanistan, but their mandate is limited to patroling Kabul and training Afghan forces.

"The contribution that Turkey has made to the Afghan mission has been tremendously important for many, many years," James Jones, Obama's national security advisor, said Friday.

"We appreciate any contribution Turkey will be able to make in order to fulfil its very important mission in the capital region of Kabul," he said.

Turkey refuses to fight Islamist insurgents and drug traffickers, wary of confronting fellow Muslims in a country with which it has close historic ties.

It says more should be done for reconstruction and improving public services to win over the Afghan people and argues its army is already under strain, fighting a bloody 25-year Kurdish insurgency in the southeast.

A recent drive by Erdogan's government to expand Kurdish freedoms and encourage the rebels to lay down arms is also expected to be discussed at the White House.

US and Iraqi support is crucial against the rebels as an estimated 2,000 of them are based in mountainous hideouts in neighbouring northern Iraq.

"The bargaining on Afghanistan is linked directly to Iraq since Obama essentially wants to pull out from Iraq and move his forces to Afghanistan," political analyst Rusen Cakir wrote in the Vatan daily.

"If the US withdraws from Iraq without taking the necessary measures, the risk for Turkey will become more serious," he said.

Since 2007, the US has backed Turkish air raids against rebel bases across the border by providing intelligence on militants' movements.

Another major issue of common interest is Iran, but Turkey's growing ties with Tehran and Erdogan's defence of its nuclear programme have raised questions on whether Ankara is deviating from its traditionally pro-Western path.

Erdogan, whose party hails from a now-banned Islamist movement, has played down concerns that its eastern neighbour may be developing an atomic bomb and slammed Western powers for turning a blind eye to Israel, widely considered the Middle East's sole if undeclared nuclear power.

Ankara insists the row with Iran should be resolved peacefully and has sought to help mediate a settlement.

Turkey's warming ties with Iran and other countries frowned upon by the West such as Libya, Sudan and Syria, have come against a backdrop of a sharp downturn in relations with Israel, its main regional ally.

Angry over the devastating war on the Gaza Strip at the turn of the year, Turkey excluded Israel from joint military drills in October, prompting harsh reactions from the Jewish state and a rebuke from Washington.

The government rejects criticism it is sliding away from the West and says it is committed to Turkey's European Union membership bid, strongly backed by Washington but opposed by some key European nations.

Obama and Erdogan are expected to discuss also Turkey's fence-mending efforts with historic foe Armenia and the long-standing Cyprus conflict, a major obstacle for Turkey's EU bid.