Prime Minister John Key visited UAE prime minister Mohammed bin Rashid Al Maktoum in Dubai ahead of his trip to Saudi Arabia.

Prime Minister John Key rejected comparisons between Saudi Arabia's justice system and public beheadings by Islamic state, ahead of a historic visit this week

On the first visit by a New Zealand prime minister, Key's priority is securing a free trade pact but criticism of the authoritarian regime's human rights record could overshadow the talks in Riyadh on Wednesday.

"We will be talking to them about [human rights]. I am obviously the first New Zealand prime minister to go to Saudi Arabia so that puts me in the position to absolutely be able to make that point to the senior leadership," Key said.

CHRIS SKELTON Prime Minister John Key takes in the sights of Dubai.

More than 50 people have this year been killed by the regime, which leaves corpses on public display as a gruesome crime deterrent.

Key previously said of Islamic State: "I will not, will not, stand by while ...people are out there being beheaded."

The Saudi government defends its use of the death penalty as justice is carried out in line with Islamic religious (Sharia) law.

Chris Skelton John Key visits the Spinney supermarket in Dubai, which stocks 78 New Zealand products.

Floggings and the amputation of limbs are used as punishment.

In January, footage showing Burmese woman Layla bint Abdul Mutaleb Bassim dragged down the street to her death shocked the world. Accused of killing her six-year-old stepdaughter, Bassim was thrown to the ground in the holy city of Mecca. As she screamed her innocence, a curved sword, swung by an executioner in traditional white robes, severed her head.

In February, Key said he would not stand by while "people are out there being beheaded", as he pushed the case for a military role in the fight against Islamic State.

"We have to acknowledge that we are different countries and different cultures. We are opposed to the death penalty and their laws have the death penalty. In the case of ISIL they don't act within the laws of their country, they are not a country. Indonesia, they have the death penalty. United States, they have the death penalty. They have a judicial process," he said.

"That's just not the case with ISIL, they are terrorists who undertake murder against people."

The Gulf Co-operation Council is New Zealand's fifth largest trading partner with $1.9 billion worth of exports a year. A deal that removes tariffs is worth at least $50m a year. Securing it hinges on Saudi support.

A trade agreement was in the works under the previous Labour Government but negotiations stalled in 2009 when New Zealand refused to lift a moratorium on live sheep exports.

In Dubai on Sunday, Key addressed a chamber of commerce event and visited a supermarket which stocks 78 Kiwi products, including cheese, chocolate and seafood. He went to Burj Khalifa, the world's tallest building, and met United Arab Emirates prime minister Mohammed bin Rashid Al Maktoum.

The UAE supports the free trade pact but "the real power base rests with Saudi Arabia", Key said.

Critics say there should be no trade-off between human rights and economic interests, particularly as New Zealand now holds a temporary seat on the UN Security Council.

"Most New Zealanders do not want us to do being trade deals with countries that behead their citizens," Green MP Catherine Delahunty.

"We should be setting ourselves better standards and drawing a line in the sand when it comes to who we are willing to sign trade deals with."

Labour's foreign affairs spokesman David Shearer said a trade boycott would have no impact on nations with a poor rights record.

"We would make no difference to those countries in terms of their actions," he said.

Amnesty International's New Zealand executive director Grant Bayldon said Saudi Arabia's justice system was "a sham."

Research published by Amnesty International last month found human rights activists were routinely harassed and ill-treated in detention and the use of torture by the security forces was widespread.

"The Saudi Arabian disrespect for human rights is absolutely breath-taking. People are held without trial, they are tortured into confessing crimes. They are convicted in shameful trials without legal support and those trials regularly end in horrific floggings, amputations and public beheadings," Bayldon said.

The advocacy group was not calling for a boycott on the trade mission but Bayldon said raising human rights violations behind closed doors was not enough.

"There is a big difference of quietly going through the motions of mentioning human rights and making it a strong focus of the trip. It really needs to be the prime minister talking about specific cases both in public and private. It can't be softly spoken behind closed doors."

BRONAGH KEY NAVIGATES THE LIMITS ON WOMEN

A top Saudi cleric was recently forced to deny he'd issue a decreed authorising men to eat their wives when faced with extreme hunger.

International media reported the bizarre fatwa without question, because the country's treatment of women is abysmal.

They have no vote (although suffrage will be extended to local elections this year), can't go out in public without a male chaperone, drive a car, enter a cemetery, try on clothes will shopping, buy a barbie doll or go for a swim. In 2012, the country's first Olympians were denounced by clerics as prostitutes.

Covering up is essential - and when Bronagh Key travels to Riyadh with her husband she will wear an abaya (loose fitting robes) and a headscarf. Michelle Obama famously defied the conservative convention when she visited earlier this year.

"We had a discussion about that. In the end, I think it is a matter of accepting and appreciating their culture... that is just a reflection of respecting their culture," the prime minister said.

"So, yep, Michelle Obama went there and didn't wear the abaya but she did completely cover herself up from the ankles to the wrists."

Bronagh Key paid a visit to Sheikha Fatima bint Mubarak Al Ketbi, mother of Abu Dhabi's Crown Prince, on Sunday. John Key said she would be talking about women's rights.

"She will be able to take the very strong track record of New Zealand - everything from two female prime minister's to the first country in the world to give women the vote."

Middle East Business Council executive advisor Michelle Boag, the other female delegate, refused to be interviewed.