India on Tuesday warned of "reciprocal measures" if the UK does not address its concerns over the new travel rules relating to Covid-19 vaccine certification with Foreign Secretary Harsh Vardhan Shringla describing these norms as "discriminatory".

External Affairs Minister S Jaishankar also took up the issue of Covishield-vaccinated travellers being required to quarantine in the UK with newly-appointed British Foreign Secretary Elizabeth Truss at a meeting in New York.

"The basic issue is that here is a vaccine, Covishield, which is a licensed product of the UK company, manufactured in India of which we have supplied five million doses to the UK at the request of the government of the UK.

"We understand that this is being used under the national health system, and, therefore, non-recognition of Covishield is a discriminatory policy and does impact those of our citizens travelling to the UK," Shringla said at a media briefing here.

Official sources said India will definitely take reciprocal measures against travellers from the UK if its concerns relating to the vaccine certification are not addressed by October 4, when the new rules will come into effect.

The foreign secretary said he has been told that certain "assurances" were being given by the UK that the issue will be resolved.

"We have also offered to some of the partner countries the option of mutual recognition of vaccination certificates. But these are reciprocal measures. We have to see how it goes. But if we do not get satisfaction we would be within our rights to impose reciprocal measures," Shringla said.

According to the new rules announced by the UK, Indian travellers who have received both doses of the Covishield vaccine manufactured by the Serum Institute of India (SII) will be considered unvaccinated and will have to undergo self-isolation for 10 days.

Developed by researchers at the University of Oxford and pharma giant AstraZeneca, Covishield is one of the two anti-Covid vaccines used by India -- Bharat Biotech''s Covaxin being the other --in its vaccination drive across the country.

The new rules have drawn sharp criticism in India with the opposition Congress urging the government to immediately intervene and ensure that there is no inconvenience faced by Indian travellers.

It is learnt that New Delhi has already issued a note verbale to the UK on the matter.

In the meeting with Truss, the external affairs minister raised the issue with her and called for resolving it at the earliest to mutual satisfaction.

"Urged early resolution of quarantine issue in mutual interest," Jaishankar tweeted after the meeting.

From October 4, the current "traffic light system" of red, amber, green countries based on levels of Covid-19 risk will be replaced by one red list of countries.

The scrapping of an amber list, which is what India is currently on, means reduced PCR test cost burden only for some travellers.

The expanded list of countries whose vaccines are recognised in the UK does not include India.

It means Indians vaccinated with Covishield would be required to undergo compulsory PCR tests as well as self-isolation.

The British High Commission on Monday said it is engaging with India to explore how it could expand recognition of Covid-19 vaccine certification issued by Indian authorities.

"The UK is committed to opening up international travel again as soon as is practicable and this announcement is a further step to enable people to travel more freely again, in a safe and sustainable way, while protecting public health," a spokesperson of the High Commission said.

"We are engaging with the Government of India to explore how we could expand UK recognition of vaccine certification to people vaccinated by a relevant public health body in India," the official added.

Former union ministers and Congress leaders Jairam Ramesh, Anand Sharma and Shashi Tharoor have slammed the UK''s travel policy, with Ramesh saying it "smacks of racism".