Chinese Premier Li Keqiang will meet EU president Donald Tusk and European Commission head Jean-Claude Juncker with hopes of forging an answer to Trump's "America First" challenge.

But years of skirmishes over trade and human rights will make a deeper alliance difficult.

The incentive to strengthen links with Beijing is strong after German Chancellor Angela Merkel, the EU's most powerful leader, on Sunday warned that the EU can no longer depend on longtime ally US as a reliable partner.

Li, China's second most powerful leader after President Xi Jinping, will also visit Germany where he will meet Merkel and sign a cooperation deal on electric cars.

"There's a lot we can offer each other," said vice foreign minister Wang Chao in the run-up to the European tour by Li.

The Brussels talks follow a tense international tour by Trump in which the unpredictable tycoon refused pleas by his European counterparts to adhere to the 2015 Paris climate accord.

The EU, US and China each roughly represent the same weight in the world economy and an exit by Washington from the climate deal would leave its only chance of survival in the hands of Brussels and Beijing.

Given the context, China's premier and the heads of the European Union's main institutions are expected to deliver a strong statement in support of the Paris agreement.

But besides climate, big obstacles to a deeper diplomatic breakthrough remain.

- 'Walk the talk' -

Also on the agenda is an EU-China investment accord that has been under negotiation since 2013 and that is largely seen as a dry run for a full trade deal.

But those talks are at a standstill over longstanding disagreements on the lack of access given to European companies in China and a fight over cheap Chinese exports that Europeans say are unfairly flooding their market.

China, the EU's second-largest trade partner, "needs to walk the talk," said EU Trade Commissioner Cecilia Malmstroem at a business conference last week.

"The welcome commitments from China about liberalisation have not been matched by concrete action," she added.

Many had hoped that President Xi Jinping's fervent defence of globalisation at the World Economic Forum in January would signal a new open trade era for China.

"We have heard a lot of positive signals coming out of China when it comes to market opening and freer trade, but we hope this week we will lead to some concrete result," the European Chamber of Commerce's Mats Harborn told Bloomberg TV.

But Li Chenggang, assistant minister of commerce, told a news briefing in Beijing that "the two sides don't see eye to eye on all issues".

China's militarisation of islands in the South China Sea and the increase in authoritarianism under Xi have also rung alarm bells for Europeans.

"EU leaders need to make good on their pledges and make human rights and the freeing of peaceful activists a top strategic priority in the EU's relationship with China," said Human Rights Watch's EU director Lotte Leicht.

In a letter to Juncker and Tusk, several groups of rights activists, including Human Rights Watch, urged the EU to take up these concerns with China's leadership.

"While EU officials are willing to engage in very public, critical battles with China over steel tariffs, solar panels, or the South China Sea, most EU officials are not willing to engage publicly in such debates over China's use of torture and arbitrary detention," the letter said.