Australia has agreed to expand its training work in Iraq to include not just the army but also law enforcement authorities.

Prime Minister Malcolm Turnbull announced the change in role following a request from the United States and Iraq for extra help, and after his talks on Tuesday with visiting US Vice-President Joe Biden. At their joint news conference Biden said: “Your folks are the best trainers in the world.”

Australia has 300 personnel in the building partner capacity mission at Taji, training Iraqi army personnel; an 80-strong special operations task group providing advice and assistance to the Iraqi counter-terrorism service, and 400 personnel in the air task group operating against Islamic State (IS) in Iraq and Syria.

Turnbull and Defence Minister Marise Payne said in a statement that the mission at Taji had been limited to training army personnel but as more areas were liberated from IS “strong and effective policing and enforcement to maintain security is required”.

The Iraqi federal and local police and border guard forces would have a key role in defending, holding and stabilising liberated areas. “Helping train these law enforcement agencies to hold and stabilise territory will assist Iraq to take responsibility for its own security and provide security for Iraq’s citizens as they return to their cities,” they said.

Australia will also increase the flexibility of the mission based in Taji so its forces can conduct training at other coalition training locations when needed.

These activities will not involve expanding personnel.

But the government has authorised the deployment of another 15 Australian Defence Force personnel to provide a counter rocket, artillery and mortar capability at Taji – this is now being provided by another Coalition member.

There have been recent announcements of expanded contributions from the US, United Kingdom, Canada, New Zealand, Italy, Spain, Denmark and Norway.

Turnbull said his talks with Biden also covered the importance of the rule of law in the South China Sea, with the US and Australia encouraging all parties to resolve their differences in accordance with international law and through peaceful negotiations.

The Trans Pacific Partnership was discussed, which Turnbull described as “a great free trade agreement”. He said that Australia awaited the approval of Congress for it. “We know that while there are political obstacles, the eloquence of the Vice-President and the President, all of the wiles he’s developed over so many years in the Congress, all of that political capital is going to be brought to bear to bring the TPP home in the Congress.”

Biden told a business audience on Monday: “It’s going to be hard to pass in both our countries, maybe not as hard for you, we’re going to try do a lame duck session in the US congress.”

If this administration doesn’t get the TPP through its chances are bleak, with Donald Trump opposed and Hillary Clinton saying she would renegotiate it.