SYDNEY - Australia has formally rejected a request from the United States for more military help to tackle the Islamic State group, arguing it had already made a “substantial” contribution to the fight.

US Defence Secretary Ash Carter in December asked coalition partners battling the militants and other militants in Iraq and Syria for a greater commitment following the Paris attacks in which 130 people were killed.

Prime Minister Malcolm Turnbull signalled at the time that there was no appetite for such a move and Defence Minister Marise Payne said Australia’s current commitment was sufficient.“Australia has considered the request from US Secretary of Defence Ash Carter in light of the substantial contributions we are already making to train Iraqi security forces and to the air campaign,” she said in a statement late Wednesday. “The government has advised Secretary Carter that our existing contributions will continue.”

The decision comes just days ahead of Turnbull meeting US President Barack Obama in Washington on a trip focused on terrorism and territorial disputes. During the visit, he will deliver a national security address at the Centre for Strategic and International Studies.

Australia has some 780 defence personnel in the Middle East supporting its operation against IS and has been active in Iraq for months.

Many are based in Iraq with 400 attached to the Air Task Group flying six F/A-18 Hornets on bombing missions.

Another 300 are in Baghdad helping train Iraqi security forces while 80 are advising and assisting on counter-terrorism operations with the Iraqi military.

Meanwhile, President Barack Obama, in a phone call with Russian President Vladimir Putin on Wednesday, emphasized the need to work toward a diplomatic solution to the crisis in Ukraine and address the conflict in Syria, the White House said.

Obama told Putin that a key next step in resolving the Ukrainian crisis was for all sides to agree on the modalities of local elections in the Donbas region of Ukraine, the White House said in a statement.

The two leaders also “noted the necessity of taking steps to foster productive discussions between representatives of the Syrian opposition and regime under United Nations auspices, principally by reducing violence and addressing the urgent humanitarian needs of the Syrian people,” the statement said.

Meanwhile, a convoy carrying desperately needed food and medicine headed to the hunger-stricken Syrian town of Madaya on Thursday, the second delivery of aid this week after months of government siege.

Dozens of trucks carrying flour and other essentials left Damascus early in the morning for Madaya, where the United Nations says suffering is the worst seen in the nearly five-year-old war.

The town’s 40,000 residents have endured a crippling siege by pro-government forces that has drawn sharp condemnation from the UN and world powers.

More than two dozen people have reportedly starved to death there since December, sparking a global outcry.

A spokesman for the International Committee of the Red Cross said that a convoy of 44 aid trucks was travelling from Damascus to Madaya.

“The priority is wheat flour and washing materials,” Pawel Krzysiek told AFP.

Medical teams were aboard the trucks and “the ICRC is also bringing a nutritionist for a proper assessment” of residents, he said.

A separate convoy of 17 trucks left the capital for Fuaa and Kafraya, two towns in Syria’s northwest encircled by rebels, and the aid will enter all three places simultaneously, Krzysiek added.

It follows a delivery on Monday that was the first humanitarian assistance received by Madaya in nearly four months.

The UN’s Office for the Coordination of Humanitarian Affairs said a third delivery to the towns would take place “in the following days.”