Donald Trump’s ambassador to Ireland warned the Government last year that businesses had begun moving their future investments out of Ireland.

As Taoiseach Micheál Martin attended a day of events intended to promote US-Ireland business links in Washington on Monday, Department of Foreign Affairs (DFA) files released under freedom-of-information laws show that during a meeting with Tánaiste Simon Harris last July, US ambassador Edward S Walsh “referred to contacts in business who are moving their investment pipeline out of Ireland”.

The documents, drawn up by Irish officials, show that Walsh told Harris, then minister for foreign affairs, this included “data centres due to future energy needs” and that he “also referred to planning-related challenges”.

In response, the Tánaiste told Walsh that Ireland was developing a new liquefied natural gas facility, and flagged reforms to planning laws.

Harris agreed to give Walsh a note on Ireland’s proposed approach to infrastructure – particularly water, power and housing – before the ambassador returned to Washington the following month.

The exchange is detailed in correspondence between the DFA and its counterparts in the Department of Housing, which released the emails to The Irish Times.

Files that give insight into ambassadorial thinking are seldom made public.

Housing officials were tasked with drawing up a “non-paper” – an informal summary of policy thinking in a given area – for Walsh, who was “expected to meet with contacts in the private sector” on his return to the US.

DFA officials told the Department of Housing “we’re trying to equip him with topline messaging about Irish investment plans” – adding that similar “non-papers” would be prepared on EU trade and tariffs and on the Middle East.

Walsh attended a St Patrick’s Day function with the Taoiseach in Washington on Monday hosted by Amazon, which has developed large data centres in Ireland. Officials said he had been “very engaged in promoting two-way trade and [was] positive on the opportunities and growth” at St Patrick’s Day events.

While Amazon received planning permission for three data centres in north Dublin late last year, it has also reportedly decided against building some similar projects here, and scrapped plans to build a large industrial plant because it could not secure an electricity supply for the project.

The US embassy in Dublin had no comment on Monday.

Speaking to journalists in advance of his meeting with Trump on Tuesday, Martin declined to be drawn on his preparations or speculate about their discussions.

“Life is unpredictable. Politics is unpredictable and so I’m enjoying what I’m doing today,” he said.

“I’m focused on the functions I have today, and then we take tomorrow when it comes. I’m looking forward to it … I’m looking forward to meeting the president. Looking forward to meeting the vice-president. And I’m looking forward to lunch on the Hill … So that’s the frame of mind.”

Nonetheless, officials admit to anxiety in advance of the meeting, with the Irish side fearing a broadside from Trump about the EU to which the Taoiseach may feel obliged to respond, perhaps setting the meeting on an unpredictable trajectory.

The meeting is overshadowed by the continuing war in the Gulf, with Trump stepping up his requests for other countries to help keep the Strait of Hormuz open to shipping. On Monday, the Taoiseach said any military intervention was a matter for Nato, of which Ireland was not a member.

He added: “We’re not a military power. We don’t have that offensive military capacity in any shape or form. So obviously that’s not something that’s on our agenda.”