Secretary of State Mike Pompeo has promised that the US is doing everything it can to free pastor Andrew Brunson.

Brunson has been held for nearly two years in Turkey on espionage and terrorism-related charges – charges he denies. He was arrested in the southwestern city of Izmir, where he had spent more than two decades doing mission work.  The pastor was recently moved from a prison to house arrest as his trial continues.

Speaking at the Values Voter Summit, which is attended mostly by Christians, Pompeo said the pastor's plight was important to the Trump administration and that their goal was to bring him home. 

'We are sparing no effort to return Pastor Brunson home to the United States,' he said.

'The work is important. He has been wrongly held and his proper place is to be able to return here to once again practice his faith in our great nation.'

The summit was also joined by Brunson's daughter Jacqueline Furnari, who rejected Turkey's charges against her father.

'The entire last two years has really shown that this is just baseless charges,' she said. 'It's a sham trial and my dad is being used as a bargaining chip and suffering for Jesus Christ.'

The next court hearing in Brunson's trial is on October 12.

Furnari added: 'It's been a painful time and we're just ready for it all to be over.'

Brunson's trial has sparked a diplomatic row between Turkey and the US, with the latter increasing trade tariffs and imposing sanctions on two diplomats.

US president Donald Trump recently said he was 'very disappointed' with Turkish President Recep Tayyip Erdogan over his refusal to free Brunson after Trump apparently helped in the release of a Turkish citizen detained in Israel.

'I'm disappointed in him,' Trump told Bloomberg, adding that Brunson's release was 'too dear to my heart.'