Barack Obama and US lawmakers ratcheted up the pressure on the Islamic State Wednesday, with the president declaring there was no hiding place for the jihadists and warning: "Our reach is long."

After Obama spoke at MacDill Air Force Base, the House of Representatives voted 273 to 156 to approve his plan to train and equip moderate Syrian rebels, a key part of his strategy to destroy the IS group.

Obama was keen to project a sternly determined mood at the Florida air base, the headquarters of US Central Command, which oversees military action in the Middle East.

He met military commanders to discuss how to defeat the so-called "Islamic State" group -- a powerful extremist organization -- while keeping America out of another protracted conflict in the Middle East.

Obama has consistently said he will not put US "boots on the ground" despite the IS organization -- which the US estimates has 20,000 to 31,000 fighters -- grabbing vast areas of Iraq and Syria in a offensive that has seen beheadings and forced religious conversions.

Two American reporters and a Briton were executed on camera by a masked IS militant, provoking revulsion and condemnation.

Obama, who last week vowed to "degrade and ultimately destroy" the IS group, stood firm on his pledge that a US combat mission was not in the cards -- but insisted the jihadists would be defeated.

"The American forces that have been deployed to Iraq do not and will not have a combat mission," Obama stressed.

His comments came after America's top officer General Martin Dempsey suggested military advisors might provide counsel to Iraqi troops in "close combat," sparking hand-wringing in Washington about "mission creep."

"Our reach is long. If you threaten America, you will find no safe haven. We will find you eventually," Obama said.

Last week he ordered expanded air strikes against the IS organization in Iraq and said the US was prepared to launch air raids on the militants in neighboring Syria.

He again emphasized the broad-based nature of the US-led coalition to defeat the jihadists, and noted that Saudi Arabia had agreed to host a US mission for training moderate Syrian rebels.

Some 40 countries are backing the coalition to defeat IS, but there was a prominent dissenting voice in the form of Iran, with President Hassan Rouhani criticizing Washington's refusal to send in ground troops.

- House backing -

In Washington, lawmakers voted to authorize the training and arming of vetted Syrian rebels to combat the Islamist radicals, a move Obama hailed as "an important step forward."

Lawmakers backed the president despite the misgivings of war-weary Democrats that the move could open the door to full-blown American intervention and concern from conservatives that the plan falls short of what is needed.

The measure was included as an amendment to a stop-gap federal spending measure which also easily passed the Republican-dominated House.

The overall bill now shifts to the Senate, where leaders are confident it will pass on Thursday and head to the president for his signature.

Expanded air strikes are already turning up the heat on Islamic State fighters, who have declared a "caliphate" straddling Iraq and Syria and claimed leadership of a global anti-Western jihad.

US forces carried out seven air strikes Tuesday and Wednesday in Iraq, Central Command said, using what it called "a mix of fighter, attack and remotely piloted aircraft."

Four of the strikes were southwest of the capital Baghdad, destroying several small IS ground units and a small boat on the Euphrates River that was re-supplying rebel forces in the area.

The US has carried out 174 air strikes in Iraq since early August but the mission has taken US aircraft close to the skies over Baghdad in recent days for the first time.

Meanwhile Western governments are facing an uphill battle trying to squeeze the finances of Islamic State jihadists, as the extremists generate cash from extortion, kidnapping and smuggling of both oil and antiquities in the large area they hold in Syria and Iraq, analysts say.

- Fierce fighting -

The combination of local forces and US air power appears to be having some success, apparently forcing top IS leaders to cross the border back into Syria, the organization's main base.

Iraqi military and tribal leaders reported several IS targets were hit in an area just south of Baghdad dubbed the "triangle of death," killing at least four militants on Tuesday.

Fierce fighting also broke out in the Jurf al-Sakhr area just a few dozen kilometers from Baghdad, and renewed clashes Wednesday left at least eight soldiers dead, an officer and an army medic said.

Jurf al-Sakhr is key because it sits on the Euphrates between the major Sunni insurgent bastion of Fallujah, west of Baghdad, and the country's most revered Shiite holy sites south of the capital.

A leader from the local Janabi tribe and an army lieutenant said the government counter-offensive was led by the Golden Brigade, which is widely recognized as the best force in the country.

Critics say it may be the only credible fighting force in what is sometimes derided as "a checkpoint army."

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