Mr Macpherson said he had spoken to Mr Hurd about an “extraordinary level of demand” on police force resources across the UK.
He said US President Donald Trump’s visit, the Royal International Air Tattoo and “large” summer events were adding to “increased pressure”.
He tweeted: “He [Mr Hurd] has reassured me the current approach to policing cordons, in relation to the ongoing major incidents in Amesbury and Salisbury, is under review to help me ensure that policing services more widely across Wiltshire and Swindon remain unaffected.
“Wiltshire Police has received great support from almost every police force across the county since the first major incident was declared in March. Alongside the Chief Constable I couldn’t be more grateful for the help and support of those forces, however with more and more rest days being cancelled and annual leave requests being put on hold, we must now explore a different approach.”
His comments came as police removed a cordon and reopened a road following an incident involving a man in his 30s outside the Zizzi restaurant in Salisbury.
“We are pleased to report that the cordon in place in Castle Street, Salisbury, has been removed and the road has been reopened,” Salisbury Police said.
Officers had been dealing with an incident involving a man outside the Zizzi restaurant where former spy Sergei Skripal and his daughter Yulia dined before falling ill.
In a tweet, the police said “at the moment there is nothing to suggest any wider risk to the public”.
An eyewitness who asked not to be named said the man involved in the incident was a “local homeless guy” who was “sat on the floor, completely conscious, talking”.
The police, who were called to the scene at 6.20pm on Thursday, said the man has been taken to Salisbury District Hospital and fully assessed by medical staff.
“We can now confirm that there is no concern for either his health or any wider risk to the public,” police said.
“We understand that our initial response to the incident may have looked alarming, but we hope you appreciate why we needed to take this highly precautionary measure. We thank you all for your patience and understanding,” they added.
A photo shared on social media earlier showed a road shut in the city centre, with the poster saying a tent was being erected on the road.
Members of the emergency services had been seen putting on protective clothing.
The pair appear to have accidentally come into contact with the same nerve agent used against the Skripals in March.