US officials watched with growing concern on Friday as reports suggested Pakistan was massing troops to the India border. "We hope that both sides will avoid taking steps that will unnecessarily raise tensions during these already tense times," said White House spokesman Gordon Johndroe. U.S. military leaders have been urging both India and Pakistan to exercise restraint in the wake of the Mumbai attacks that many believe originated with Pakistan-based militants. U.S. intelligence and military officials were still trying to determine if the reported troop movements were true, and, if so, what Pakistan's intent may be. Officials spoke on condition of anonymity to discuss intelligence matters. One senior military official on Friday said that the U.S. is monitoring the issue, but still could not confirm assertions from Pakistani intelligence officials that some 20,000 troops were on the move, heading to the Indian border. A key concern for U.S. officials is that some of those troops may have been stationed along the volatile Afghan border, and were being diverted to the Indian side. Defence Secretary Robert Gates and Mullen, who have both been in the region in recent weeks, have expressed the hope that Pakistan would stay focussed on fighting militants in its mountainous northwestern areas. There was also no indication on Friday that either Gates or Mullen had reached out to their counterparts in Pakistan since these latest reports had surfaced. Johndroe added that, "We continue to be in close contact with both countries to urge closer cooperation in investigating the Mumbai attacks and in fighting terrorism generally."