Tehran is under scrutiny from the international community for allegedly using civilian nuclear work to hide a weapons program. The Iranians deny the allegations.
British Foreign Secretary William Hague in statements Wednesday before the House of Commons said there were emerging concerns about Iranian military activity.
He accused Iran of helping its allies in Syria with suppressing an anti-government movement in the country.
"Iran has also been carrying out covert ballistic missile tests and rocket launches, including testing missiles capable of delivering a nuclear payload in contravention of U.N. Resolution 1929, and it has announced that it intends to triple its capacity to produce 20 percent enriched uranium," Hague said. "These are enrichment levels far greater than is needed for peaceful nuclear energy."
Victoria Nuland, a spokeswoman for the U.S. State Department, said Washington has reason to be concerned about Iranian missile activity.
"It's time for Iran to take steps to be transparent with the international community and to come back into compliance with U.N. Security Council resolutions," she said.
Resolution 1929 prohibits Iran from activity tying nuclear material to its ballistic missile technology.
Iran announced earlier Tuesday it had successfully fired 14 surface-to-surface missiles on the second day of its Great Prophet 6 military drills. Iranian commanders said Israel and U.S. bases in the Middle East are within range of the missiles.