Expressing ignorance about the contents of the letter written by some Senators to the Prime Minister against Indo-Iran ties, the Bush administration said it continues to discuss the issue with New Delhi.

"...we have not seen this letter and I'm not sure whether the Indians have had a chance to look at it and react to it," Deputy spokesman Tom Casey told reporters in Washington when asked to comment on the strong-worded letter that speaks of risks to the civil nuclear deal if New Delhi did not back off from its engagement with Tehran.

"In terms of what we say and while what we have discussed with our Indian counterparts, I know that we have raised Congressional concern about their (India's) cooperation with Iran," he said.

Casey said the US continues to "encourage the Indians to use what influence they have with the Iranians to press them to comply with UN Security Council Resolutions and to behave responsibly in a wide variety of areas."

He said when Foreign Secretary Shivshankar Menon was here earlier this week meeting senior officials like Under Secretary of State for Political Affairs Nicholas Burns and others, he has had some "fairly strong" views on the subject.

"But certainly this is an issue that we continue to discuss with them in our official contacts as well," he added.

The strong-worded letter from Capitol Hill came from senior lawmakers like Tom Lantos, Chairman of the House Foreign Affairs Committee; Ileana Ros-Lehtinen, the ranking Republican; Howard Berman; Gary Ackerman, who is the Chair of the House Middle East and South Asia subcommittee, and others.

The letter angered the UPA government's Left allies and opposition BJP who dubbed it as an "open threat" and interference in India's internal affairs.

In their letter, the Senators said, "Regarding Iran, we are deeply concerned by India's increasing cooperation with that country, including the exchange of visits between high-level officials, enhanced military ties, and negotiations of agreements to establish closer economic relations."

Detailing the interactions New Delhi has had with Tehran, it said these have a "significant potential to negatively affect relationship between the US and India in general and consideration by Congress of the 123 Agreement in particular."

The Senators said, "Such cooperation raises renewed questions about the possible diversion of sensitive technology to Iran, for which Indian entities have been sanctioned in recent years, including US-origin technology provided to India in the context of civilian nuclear and space cooperation."