France's Bureau Veritas, which verifies the safety and environmental standards of ships, has stopped its marine work in Iran, the classification society said in a new setback for Tehran as it faces growing pressure from Western sanctions.

Without the necessary verification from such bodies, ships are unable to call at international ports. The move follows a similar decision in April by British classification society Lloyd's Register to halt operations in Iran.

'The only marine-related activity that Bureau Veritas has ever exercised onboard vessels in Iran or owned by Iranian companies is classification surveys, which are only dealing with safety and maritime pollution prevention, that is, for safety and protection of third-parties' interests,' it said in a statement on Thursday.

'Nonetheless...Bureau Veritas has taken the decision to cease all marine activities on Iranian-owned vessels with a view to alleviating any type of confusion.'

Iran faces mounting sanctions over its disputed nuclear programme, which Western countries suspect is aimed at developing arms but which Tehran says is for peaceful purposes.

Classification societies are hired by ship owners to regularly check that vessels, from their hull and propulsion systems to the machinery and appliances, meet international safety standards. Under international conventions, it is required for a ship to be classed when docking at major ports.

Lloyd's Register told Reuters in April it had stopped assessing around 60 tankers and container ships owned by the National Iranian Tanker Company (NITC) and Islamic Republic of Iran Shipping Lines (IRISL) following pressure from the United States.

It is likely that Iran is already securing cover from Asia-based classification societies, shipping industry sources say.

US-based United Against Nuclear Iran (UANI), which has been among pressure groups opposed to the Islamic Republic's nuclear ambitions, said it had urged Bureau Veritas to stop providing cover for Iranian vessels.

In a letter addressed to UANI this week, Bureau Veritas said that following discussions with French government authorities it had decided to 'disengage completely' from all marine activities related to Iran.

Bureau Veritas added that it given notice to Iran's flag authority at the end of 2011 of the termination of the agreement 'of delegation of statutory inspection and certification surveys for Iranian registered vessels'.

It said it had notified IRISL in May 2012 that it was ceasing all services for IRISL and its subsidiaries, irrespective of their flags. IRISL has been on a Western blacklist of sanctioned entities for a number of years.

'Bureau Veritas has also taken the same decision with respect to the National Iranian Tanker Company (NITC) for all their vessels and has decided to cease all marine activities in respect of all other known Iranian shipping companies' vessels,' it said in the letter.

NITC faces the prospect of potential sanctions after the U.S. senate passed a bill last month that aims to target Iran's biggest tanker operator. NITC lost its ship insurance cover from European providers last year due to the sanctions.

It secured alternative insurance cover mainly in Asia and also in Iran.

Pressure group UANI, which had previously said Bureau Veritas's certification activities were in violation of EU sanctions, welcomed the move.

'We accept Bureau Veritas's pledge to end all of its marine activities related to Iran,' said UANI chief executive Mark Wallace, a former US ambassador.

'The international community must focus specifically on the shipping industry, to deny the Iranian regime access to global trade and seaborne crude oil exports,' he added.-Reuters