US President Barack Obama is to set out his "game plan" against Islamic State militants in a speech on Wednesday.

Mr Obama, who has been criticised for failing to outline a strategy, told NBC TV the US would degrade IS, shrink their territory and "defeat them".

US jets bombed IS targets in western Iraq for the first time on Sunday.

Meanwhile, the Arab League has vowed to take "all necessary measures" against IS, which has seized a huge amount of territory from Iraq and Syria.

The league gave its backing to a Security Council resolution passed last month calling on member states to stem the flow of weapons and money to extremists in Iraq and Syria.

BBC World Service Middle East editor Sebastian Usher says the Arab League's message will hearten Mr Obama, but the question now is whether its members will fully act on it, and act together rather than against each other.

Speaking on NBC's Meet the Press, Mr Obama said: "I'm preparing the country to make sure that we deal with a threat from Isil."

IS, also often referred to as Isil or Isis, has taken over large swathes of Iraq and Syria in recent months, declaring the land it controls a "caliphate".

Mr Obama went on: "On Wednesday, I'll make a speech and describe what our game plan's going to be going forward."

He said he would "start going on some offence" against IS.

But the strategy was "not going to be an announcement about US ground troops", he added.

He said: "This is not the equivalent of the Iraq war. What this is, is similar to the kinds of counterterrorism campaigns that we've been engaging in consistently over the last five, six, seven years.

"I just want the American people to understand the nature of the threat and how we're going to deal with it and to have confidence that we'll be able to deal with it."

Mr Obama said the strategy would not involve the US alone but would be one pursued by an international coalition.

He said: "We are going to be able to not just blunt the momentum of Isil. We are going to systematically degrade their capabilities. We're going to shrink the territory that they control. And ultimately we're going to defeat them."

The interview was conducted on Saturday, shortly after Mr Obama returned from the Nato summit in Wales, where the grouping agreed to take on IS.

Mr Obama made his "no strategy" comment last month when asked whether he needed Congress's approval to "go into Syria".

BBC North America editor Jon Sopel says that while it showed how complex the situation in the region was, it also showed the extreme wariness of the president to unilaterally start military action when it was not clear where it would end.

The US military said Sunday's five strikes involved bomber and fighter aircraft and were in support of Iraqi security forces and Sunni tribes protecting the Haditha dam - a major source of energy in Iraq.

It said militants' armoured vehicles, some carrying anti-aircraft artillery, were destroyed. The US said all its aircraft left the area safely.

Iraqi troops and militia also retook Barwana, east of Haditha, from the jihadists, an AFP correspondent reported.