As Republican leaders in Congress prepare to block Syrian refugees from the United States, one legislator proposed requiring three national security chiefs to certify personally that each refugee admitted from Iraq or Syria is not a threat.

The Republican chairman of the House of Representatives homeland security committee, Michael McCaul, said his bill would strengthen security measures for all refugee populations seeking to enter the United States.

It also would stipulate that no Syrian or Iraqi refugee can enter the United States until Congress receives certification that they are not a national security threat, he said in a statement late on Tuesday.

“The bill requires the nation’s top security officials — the secretary of homeland security, the director of the FBI, and the director of national intelligence — to certify before admitting any Syrian or Iraqi refugee into the United States that the individual does not represent a security threat,” Mr McCaul said.

House Republican leaders, worried about ISIS attacks after Friday’s attacks in France, on Tuesday threatened to suspend the administration’s plans to admit 10,000 Syrian refugees in the coming year.

Mr McCaul said legislation was necessary because the President was unlikely to halt the programme.

Individual certification for these refugees, who already undergo a screening process that can take between 18 and 24 months and involves multiple US security agencies, is likely to slow that process down even further.

Mr Obama, travelling in Asia, on Tuesday called attempts to block entry “offensive and contrary to American values”.Obama administration officials had held a conference call on Tuesday with 34 US governors to discuss the country’s refugee programme, the White House said, after more than a dozen governors said they would refuse to accept Syrian refugees.

The administration officials assured the governors that the refugees would undergo the most rigorous screening and security vetting of any category of traveller to the United States, the White House said in a statement.

Some of the governors encouraged further communication by the White House to ensure that they are able to better respond to questions from the public about the refugee screening and resettlement process, the White House said.