The 2019 Global Diplomacy Index, released on Wednesday by the Lowy Institute, finds China has pipped the US as the top-ranking country overall when it comes to the size and reach of its diplomatic network.

China has a total of 276 postings around the world, including embassies/high commissions, consulates/consulates-general, permanent missions and other representations, while the US has 273.

In 2016, the Global Diplomacy Index showed China was in third place behind the US and France and by 2017, it had jumped to second place.

The research tracks 61 nations, including all G20 countries, all OECD countries and most Asian countries.

The 2019 results sees France remain in third place with 267, followed by Japan with 247 and Russia with 242.

Lowy research fellow Bonnie Bley says being able to measure the diplomatic infrastructure of a country provides information about its national ambitions.

When it comes to China, the country has really boosted its number of consulates, which tend to have an economic function and facilitate economic co-operation, Ms Bley told AAP.

China now has 96 consulates compared with the US, which has 88.

"This diplomatic expansion by China is probably linked to its economic interests in particular," Ms Bley said.

This fits well with the narrative that China tends to prefer economic diplomacy over traditional diplomacy, and is well-timed for signature initiatives such as its global Belt and Road infrastructure projects, she said.

That the US has not added any initiatives on the diplomatic front "really speaks to how the current administration prefers to operate away from the wider foreign policy bureaucracy", Ms Bley said.

When it comes to President Donald Trump, there is "a lot happening on Twitter; whether you'd call that Twitter diplomacy I'm not quite sure", she said.

However, the US is still the most attractive place for other nations to locate embassies and consulates - 342 belonging to the 61 countries in the index - while China is a distant second with 256.

"That does still speak to the ongoing diplomatic clout of the US," Ms Bley said.

The research ranks Australia as 27th on the index with a total of 118 posts, which is surprisingly low for a country with its economic development and size, Ms Bley said.

Among the G20 countries it ranks 18th, ahead only of Saudi Arabia, and among OECD countries it ranks 20th.

Although Australia is slowly building its diplomatic network, it's not really enough to change our place in the rankings, Ms Bley said.

Even the federal government's plans to open five new diplomatic missions in the Pacific region would still only bump Australia up by one place in the rankings if other factors stayed constant, Ms Bley said.

Australia's diplomatic network is quite "asymmetrical", geared towards Western Europe, Northern America and Asia, with a low presence across Africa and South America, she added.

Australian Associated Press